The intelligence services “have not served the interests of the country,” Mrs. Kirchner said in the speech, in which she proposed replacing the agency, the Intelligence Secretariat, or S.I., with a new organization that would have reduced surveillance powers.

Mrs. Kirchner accused rogue factions within the S.I. of trying to sabotage an agreement with Iran to jointly investigate the attack on the Jewish center, which killed 85 people.

Before the prosecutor, Alberto Nisman, was found dead in his apartment this month, he made the explosive assertion that Mrs. Kirchner had tried to reach a secret deal with the Tehran government to shield Iranian officials from responsibility for the bombing. Her aides have accused a spymaster she ousted from the agency last month of having a hand in preparing Mr. Nisman’s criminal complaint against her and others.

In a wheelchair with a cast on her fractured left ankle, Mrs. Kirchner hinted that an aide to Mr. Nisman was responsible for his death and sought to link the aide to the Clarín Group, a news organization that has long been critical of her government.

The speech occurred as the death of Mr. Nisman has shed light on the shadowy power struggle between the government and its spies.

Mrs. Kirchner contended that Mr. Nisman had been manipulated by the spymaster, Antonio Stiusso, whose longevity and influence have been compared to J. Edgar Hoover’s.

Now the death is fueling a broader debate about whether the nation’s intelligence services need to be reined in, or whether the president’s inner circle is hoping to shift public attention onto an opaque realm it has clashed with in recent months.

“We’re finally gazing into the underworld where politics meets the security state and gangsterism,” said Federico Finchelstein, an Argentine historian at the New School for Social Research in New York. “This is one of those pivotal moments in Argentina when something subterranean emerges in a bloody fashion.”

The case has held constant surprises. With investigators still trying to determine whether Mr. Nisman was murdered or committed suicide, Damián Pachter, the first journalist to report the death, fled to Israel, saying he feared for his life in Argentina.

In an account on Monday in the Israeli newspaper Haaretz, Mr. Pachter said he concluded that he was being followed by an Argentine intelligence officer and decided to leave the country, flying to Israel by way of Uruguay and Spain.

“They are using their security forces to chase me,” Mr. Pachter told reporters in Tel Aviv when he arrived Sunday evening. “I just had to move fast and quick, as fast as I could.”

The first charges in Mr. Nisman’s death were brought on Monday. Viviana Fein, the lead prosecutor in the case, said that Diego Lagomarsino, the aide to Mr. Nisman, had lent him the .22-caliber pistol used in his death. Mr. Lagomarsino was charged with providing a firearm to somebody not licensed to use it. The assistant was quoted as saying that Mr. Nisman had asked for the pistol because the spymaster, Mr. Stiusso, had told him he was in danger.

Mrs. Kirchner also cast suspicion on Mr. Lagomarsino, accusing him of being an opponent of her government and of having family ties in an indirect way to Clarín, the media group with which the president has long sparred. She said Mr. Lagomarsino’s brother worked at a law firm representing Clarín.

In Mrs. Kirchner’s own reading of the death, Mr. Stiusso looms large. A powerful figure for decades, Mr. Stiusso served for 12 years under Mrs. Kirchner and Néstor Kirchner — her late husband and predecessor as president — before her government ousted the spymaster from the Intelligence Secretariat in December.

There seems little doubt that Mr. Stiusso worked closely with Mr. Nisman as he pursued his investigation into the 1994 bombing. In a televised interviewon Jan. 14, shortly after accusing Mrs. Kirchner’s government of trying to undermine his investigation, he acknowledged working extensively with Mr. Stiusso, saying the spy chief had “absolutely” complied with his requests for information.

But Mr. Nisman also said he had been concerned that some of the evidence from Mr. Stiusso might not hold up in court. Mr. Nisman, explaining that he used only intelligence information that was legally valid, said he sometimes told Mr. Stiusso: “Look, this evidence is wonderful for intelligence, but I have to go before a court. They’ll throw me out. What do I say?”

Mr. Nisman’s 289-page criminal complaint, released after his death last week, is based largely on intercepted calls and text messages believed to have been obtained by intelligence agents. But Mrs. Kirchner’s aides contend that intelligence officials did more than just help Mr. Nisman.

Her chief of staff argues that Mr. Stiusso fed misleading information over the course of the investigation, and questioned whether Mr. Nisman had even written the complaint accusing the president and her aides of subverting his inquiry.

The tensions with Mr. Stiusso had been building for a while. In October, one of Mr. Stiusso’s top counterintelligence agents was shot dead by members of the Falcon Group, a special operations unit of the Buenos Aires police, pointing to rising hostilities between different security forces.

A simmering power struggle within the intelligence agency, known here as S.I., moved Mrs. Kirchner to purge its leadership in December, removing the political appointees at the agency’s helm and ousting Mr. Stiusso as director of operations, according to news reports. She named a trusted former chief of staff as S.I.’s new director.

With a year left in her term, it seemed as if Mrs. Kirchner was asserting more control over the agency, potentially opening the way for greater transparency in its activities. Founded in 1946 during Juan Domingo Perón’s first presidency, the agency evolved during the Dirty War from 1976 to 1983 into a secret police force that hunted down the military dictatorship’s opponents.

“With the shift to democracy, public institutions grew more open, but the intelligence sector remained remarkably opaque, without effective controls,” said Torcuato Sozio, executive director of the Civil Rights Association, which promotes accountability. “Stiusso’s removal was viewed as a challenge to this impenetrable legacy.”

Mr. Nisman stunned Argentina with his criminal complaint, including the claim that an S.I. agent named Ramón Allan Héctor Bogado — who was quoted in an intercepted phone call revealing privileged information about the president’s health problems before they became public — had participated in efforts to reach a secret deal with Iran.

Vehemently disputing the assertion, government officials said that Mr. Bogado had never worked for S.I., describing him as a “con artist.” The government also released an email from Ronald Noble, the former secretary general of Interpol, stating that Argentine authorities had never tried to get Interpol to lift arrest warrants for Iranians wanted in connection to the attack, striking at one of the main pillars of Mr. Nisman’s complaint.

As the investigation proceeds, the cabinet chief, Jorge Capitanich, raised the possibility that rogue agents were involved in the events around Mr. Nisman’s death, describing “intelligence services representing dark interests.”

Some opponents of Mrs. Kirchner are skeptical. “How much time did the government put up with Stiusso being a double- or triple-agent?” asked Jorge Lanata, a journalist and an influential critic of the president, referring to the spymaster’s long tenure under the Kirchners. “The monsters projected in the shadows of the ceiling are getting bigger and bigger.”

No charges against Mr. Stiusso have been filed in connection to Mr. Nisman’s criminal complaint. Efforts to reach him were unsuccessful.

Amid the claims and counterclaims, Ms. Fein, the lead investigator in the Nisman death, said that the shot killing Nr. Nisman was fired while the gun was “practically resting” on Mr. Nisman’s head.

“There is no distance,” she said, disputing some reports that the shot had come from a distance of six to eight inches, a detail many Argentines had taken to mean Mr. Nisman was murdered.

Sofía Guterman, 73, a retired tutor whose daughter died in the unsolved 1994 bombing, is waiting for definitive answers.

“We knew that there were certain agents working with him,” Ms. Guterman said of Mr. Nisman. But as for the accusation that spies had manipulated him, she said, “We don’t know if it happened like that, or if the government is dreaming things up.”

**Isabel Kershner contributed reporting from Jerusalem