Shortly after the agents arrived in the spring of 2003, an Islamic militant living in Oslo known as Mullah Krekar received a warning from an anonymous Norwegian official, according to Krekar's lawyer. The message: Krekar, then head of a Kurdish insurgent group, was a CIA target and should watch his back.

The spies left Norway by the end of the summer, according to records of their travels compiled by European investigators. If the CIA was planning to abduct Krekar, like other Islamic radicals it had secretly apprehended in Europe after the attacks of Sept. 11, 2001, those plans were quietly abandoned.

But it would not be the first or last time that the U.S. government had sought to push Krekar out of Norway. For more than a decade, the Kurdish cleric had enjoyed protection in the Nordic country as a political refugee, even as he frequently slipped back into his homeland in northern Iraq to lead an armed separatist movement called Ansar al-Islam, which has carried out attacks on civilians and U.S. troops.

The case shows how the United States has struggled to deal with Islamic militants who are allowed to live freely in Europe despite being labeled serious security risks. Others have included radical clerics in London and supporters of the Hamburg cell responsible for the Sept. 11 hijackings.

But the pursuit of Krekar also demonstrates how U.S. tactics in confronting those militants have sometimes backfired, giving ammunition to critics who accuse the Bush administration of skirting the law or relying on questionable evidence.

Before the invasion of Iraq, the U.S. government publicly portrayed Krekar and his network as an organizational link between al-Qaeda and the government of Saddam Hussein. Under pressure to prove that connection, the United States tried a variety of tactics to forcibly remove Krekar from Norway and hand him over to friendly security services in the Middle East.

Each attempt failed. Today, although the Norwegian government has declared Krekar a security threat and ordered him deported, the mullah is still in Oslo.

Most evidence against him remains classified. But other charges have been refuted in court or publicly discredited, including allegations by U.S. and Iraqi officials that Krekar ordered followers to carry out suicide bombings and that Ansar controlled a chemical weapons factory.

"At first, I didn't think I had done anything that was a threat to the Americans," Krekar said in an interview. "Later, some people told me I had become a target, but I didn't think the Americans would come for me themselves. They wanted to use me, to show that there was a link between Saddam and al-Qaeda."

The intense U.S. interest in Krekar came at a time when the CIA was targeting other Islamic radicals in Europe for "extraordinary rendition," the clandestine practice of seizing terrorism suspects and transferring them to allied nations that sometimes practice torture. Among suspects grabbed by the CIA: a Muslim cleric in Milan, two Arabs living in Stockholm and two others from Germany.

The CIA and the U.S. Embassy in Norway declined to comment on whether Krekar was a rendition target. In a prepared statement for this article, State Department deputy spokesman Tom Casey said, "The United States continues to consider Krekar to be a threat to national security, and we think the same with respect to Ansar al-Islam."

U.S. officials have made no secret of their desire to see Krekar booted from his Scandinavian haven. As secretary of state, Colin L. Powell repeatedly urged his Norwegian counterparts to expel Krekar, singling out Ansar al-Islam as proof of a connection between the Iraqi government and al-Qaeda in a February 2003 speech to the United Nations.

In August 2003, a few weeks after the CIA operatives left Oslo, Attorney General John Ashcroft made his own trip to this nation of 4.6 million people to ratchet up the pressure. He called Ansar "a very dangerous group," whose leaders "merit the very close attention of those who are fighting terrorism."

Made 'Bigger Than He Is'
Krekar, whose real name is Najumuddin Faraj Ahmad, is 50 years old. Fluent in four languages and sporting a bushy black beard, he has become a celebrity in Norway. He has published an autobiography -- "My Own Words" -- and aggressively defended his reputation, saying he quit as Ansar's leader in 2002.

Even as he denies involvement in terrorism, he has praised those who practice it. In an interview with a Kurdish newspaper in June 2006, he called al-Qaeda's founder, Osama bin Laden, "a good Muslim" and wished him a long life. He also lamented the "bad news" about the recent death of Abu Musab al-Zarqawi, chief of al-Qaeda forces in Iraq. "But I am not sad, because he went to paradise," Krekar added.

Krekar has also been questioned by European counterterrorism investigators about his alleged ties to radicals in Germany, Sweden, Italy and Spain, though none of those countries has filed charges against him.

"Everyone -- the Americans, the Islamists, the Norwegian government -- has built up Mullah Krekar into someone bigger than he is, into a symbol," said Brynjar Meling, one of his Norwegian attorneys. "And he has let them do this."

Krekar hasn't always been an enemy of the United States. He fled northern Iraq in 1990 and received asylum in Norway after claiming he had been persecuted by Saddam Hussein's security services.

After the Persian Gulf War of 1991, he returned for long visits to his Kurdish homeland, which was under the protection of U.S. warplanes maintaining a "no-fly" zone. In early 2001, he said, he and other Kurdish leaders met with three CIA officers to discuss how to overthrow Hussein.

Later that year, Krekar founded Ansar al-Islam, or Followers of Islam. The network carved out a small territory near the Iranian border and engaged in skirmishes with other Kurdish factions. U.S. counterterrorism officials suspected that Ansar sheltered al-Qaeda fugitives who had fled Afghanistan after the U.S. invasion there in 2001.

In September 2002, after crossing the mountainous border with Iran, Krekar was detained by Iranian authorities and put on a flight to Amsterdam. Upon landing, he was arrested again, this time by Dutch authorities, who said he was wanted for extradition to Jordan on drug charges.

Krekar said that the allegations were trumped up and that he had never been to Jordan. His attorneys said U.S. officials had orchestrated the detention.

Dutch officials confirmed U.S. involvement in the case but didn't elaborate. "You can assume the Americans have an interest," Dutch Justice Ministry spokesman Martin Bruinsma told reporters.

While he was held in Amsterdam, Krekar said, he was questioned by FBI agents on two occasions, even though he wasn't wanted on U.S. charges. "They wanted to talk about al-Qaeda," he recalled. "I didn't answer anything. I said, 'Just ask about me and my group.' "

Krekar was released in January 2003 after Jordan failed to provide detailed evidence against him. He flew to Oslo, where authorities weren't eager to let him return but didn't have a legal basis for refusing him entry.

In U.S. Spies' Sights
Three months later, on April 24, a CIA officer arrived in Oslo on an SAS flight from New York. He checked into the Radisson SAS Plaza Hotel in Oslo, a few blocks from Krekar's apartment, and registered as an employee of a fictitious technology firm in Hyattsville, Md.

The same CIA officer, using a false cover name, had been present in Milan two months earlier for the abduction of a radical Muslim cleric, Hassan Mustafa Osama Nasr, according to Italian prosecutors.

Nasr was taken to Egypt, where he says he was tortured. Italian authorities have filed kidnapping charges against 25 CIA operatives, including the officer who later flew to Norway. None has been arrested.

The spies' European travels were reconstructed by Italian investigators who traced their frequent-flier and credit-card account records. The existence of the records was first reported by Stavanger Aftenblad, a Norwegian newspaper.

Four days after the CIA officer arrived in Oslo, Krekar's attorney, Meling, said he received a warning about his client from a Norwegian government source, via an intermediary. Although the message was vague, it made clear that U.S. spies had Krekar in their sights. In response, the lawyer wrote a letter to Norwegian police, requesting extra protection for Krekar.

The CIA operative left Norway on May 18. But two weeks later, he was replaced by a female U.S. spy -- also charged in the Italian kidnapping case -- who flew to Oslo from Chicago.

She was joined a month later by another female agent, according to Stavanger Aftenblad. Both women registered under fictitious names and businesses and rented a car for a month, the newspaper reported. Both left the country by summer's end.

What else the spies did in Norway is unknown. But at the time of their visit, their cover was jeopardized as rumors swirled about their presence in Oslo.

In May 2003, local news media reported that the Norwegian government had approved plans for undercover U.S. agents to come to Norway to investigate Islamic radicals, including Krekar. Norwegian officials would not confirm or deny the reports but said foreign intelligence agents would not be allowed to operate in the country independently.

Meanwhile, Norwegian authorities, with the aid of intelligence provided by U.S. officials, tried to deal with Krekar in other ways.

The cleric was arrested on the eve of the invasion of Iraq in March 2003 but released a few weeks later for lack of evidence. Later that year, Norwegian prosecutors opened another investigation, this time focusing on allegations that Krekar had ordered Ansar recruits to stage suicide bombings in Iraq.

The case hinged on a key witness: a would-be suicide bomber who was captured in Iraq and handed over to U.S. forces. The failed bomber told Iraqi officials that Krekar was behind the plot. When he was interviewed by Norwegian investigators in Baghdad, however, the man recanted, saying he had been tortured until he agreed to testify against Krekar.

Norwegian immigration officials have tried for years to kick Krekar out of the country. Citing classified evidence, the government first declared Krekar a threat to national security in 2003 and ordered him deported.

He has appealed to the courts, where he has lost repeatedly. On Nov. 22, an appellate court upheld the government's decision, declaring, "Reasons exist to fear that the plaintiff has links with terrorist activities and groups."

But chances are remote he'll have to leave Oslo anytime soon.

Under Norwegian law, no one can be deported to a country where he or she could face torture or the death penalty. Judges in Norway have ruled that Iraq is such a place and will probably remain that way for years.

"I think Mullah Krekar can get a mortgage and prepare for a long and secure stay in Norway," Arvid Sjoedin, another of his attorneys, said last month.