Baitullah Mehsud, who has a $5 million bounty on his head from the U.S., said Monday's attack outside the eastern city of Lahore was in retaliation for U.S. missile strikes against militants along the Afghan border.

"Soon we will launch an attack in Washington that will amaze everyone in the world," Mehsud told The Associated Press by phone.

Mehsud and other Pakistani Taliban militants are believed to be based in the country's lawless areas near the border with Afghanistan, where they have stepped up their attacks throughout Pakistan.

The Pakistani Taliban leader also claimed responsibility for a suicide car bombing that killed four soldiers Monday in Bannu district and a suicide attack targeting a police station in Islamabad last week that killed one officer.

Such attacks pose a major test for the weak, year-old civilian administration of Pakistani President Asif Ali Zardari that has been gripped with political turmoil in recent weeks.

The gunmen who attacked a police academy in Lahore killed seven police and two civilians, holding security forces at bay for about eight hours before being overpowered by Pakistani commandos. Some of the attackers wore police uniforms, and they took hostages and tossed grenades during the assault.

Earlier Tuesday, a spokesman from a little-known militant group linked to the Pakistani Taliban also claimed credit for the police academy attack and a similar ambush-style attack against the Sri Lankan cricket team earlier this month in Lahore.

Omar Farooq, who said he is the spokesman for Fedayeen al-Islam, said the group would carry out more attacks unless Pakistani troops withdraw from tribal areas near the Afghan border and the U.S. stops its drone strikes. The group previously said it was behind the deadly September bombing of the Marriott hotel in Islamabad that killed 54 people.

The Pakistani Taliban has links with al-Qaida and Afghan Taliban militants based in the border region between the two countries who have launched attacks against U.S. and NATO forces in Afghanistan.

Pakistan faces tremendous U.S. pressure to eradicate militants from its soil and has launched several military operations in the Afghan border region.

The U.S. has stepped up drone attacks against militants in the area, causing tension with Pakistani officials who protest they are a violation of the country's sovereignty and kill innocent civilians.

Monday's highly coordinated attack highlighted that militants in the country pose a threat far outside the border region. It prompted Malik, Pakistan's top civilian security official, to say that militant groups were "destabilizing the country."

The gunmen killed six police during the assault, and one died late Monday from his injuries, said Lahore's commissioner, Major Azam Khan. He said Tuesday that the initial investigation revealed that two civilians were also shot and killed, but he did not reveal their identities.

More than 90 officers were wounded in the assault, according to officials.

After gunmen stormed the academy, masses of security forces surrounded the compound, exchanging fire in televised scenes reminiscent of the militant siege in the Indian city of Mumbai in November and the attack on Sri Lanka's cricket team.

Khan said three of the attackers blew themselves up when commandos retook the police academy to avoid arrest.

Wasim Ahmad Sial, a senior Lahore police official, said authorities have obtained fingerprints of the attackers who blew themselves up and have determined one of their identities. He did not provide further details.

Punjab police chief, Khawaja Khalid Farooq, told reporters Tuesday that a suspected militant who was captured at the scene of the attack had provided "genuine and actual leads that are beneficial for interrogation."

He said about 50 other people in Lahore were detained overnight for questioning.