BAGHDAD, Iraq (AP) – U.S. and Iraqi forces killed 104 insurgents in hundreds of raids since terrorist leader Abu Musab al-Zarqawi was slain last week, and the American death toll in the war in Iraq hit 2,500, the U.S. military said Thursday.

Even as the Iraqi government released a document found in al-Zarqawi’s hideout that appeared to show the insurgency was weakening, new violence erupted. Gunmen shot and killed 10 Shiites in Baqouba, northeast of Baghdad.

U.S. officials also identified the man claiming to have succeeded al-Zarqawi as head of the al-Qaida in Iraq terrorist group as Abu Ayyub al-Masri, an Egyptian with ties to al-Qaida.

American and Iraqi forces have carried out 452 raids since the June 7 airstrike on al-Zarqawi, and 104 insurgents were killed in those actions, said U.S. military spokesman Maj. Gen. William Caldwell.

The nationwide raids led to the discovery of 28 significant arms caches, Caldwell said.

He said 255 of the raids were joint operations, while 143 were carried out by Iraqi forces alone. The raids also resulted in the captures of 759 “anti-Iraqi elements.”

The Pentagon’s announcement that 2,500 U.S. troops had died since the war in Iraq began more than three years ago did not include any details on when the grim milestone was reached.

The grim milestone underscored the continuing violence in Iraq, just as an upbeat President Bush returned Wednesday from Baghdad and refused to give a timetable or benchmark for success that would allow the 132,000 U.S. troops to come home.

According to the Pentagon totals, 1,972 service members have been killed in action in Iraq, and another 528 died from other non-hostile causes. There also have been 18,490 troops wounded in action, including 8,501 who did not return to duty.

The 10 Iraqi men killed Thursday were pulled off a bus in Baqouba near where al-Zarqawi was killed. The 10 men _ nine workers at the city’s industrial area and the driver _ were between the ages of 20 and 45 and were heading back to their homes, a police officer said on condition of anonymity because he was not authorized to speak to the media.

The workers included three brothers and six other relatives. The gunmen sped away in two black sedans, the officer said.

Caldwell said al-Zarqawi’s successor apparently is the same person as a man identified by the nom de guerre Abu Hamza al-Muhajer who has claimed to have succeeded al-Zarqawi and vowed to avenge him in threatening Web statements in recent days.

The Afghanistan-trained Al-Masri, an explosives expert, was a key figure in the al-Qaida in Iraq network and was long responsible for facilitating the movement of foreign fighters from Syria into Baghdad, Caldwell said at a news conference.

Al-Masri has been a terrorist since 1982, “beginning with his involvement in the Egyptian Islamic Jihad,” which was led by Osama bin Laden’s deputy, Ayman al-Zawahri, Caldwell said.

Authorities said a document found in al-Zarqawi’s hideout that includes a blueprint for trying to foment a war between the United States and Iran and also appears to show that the insurgency in Iraq is weakening.

The document said the insurgency was being hurt by the U.S. military’s program to train Iraqi security forces, by massive arrests and seizures of weapons, by tightening the militants’ financial outlets, and by creating divisions within its ranks.

“Generally speaking and despite the gloomy present situation, we find that the best solution in order to get out of this crisis is to involve the U.S. forces in waging a war against another country or any hostile groups,” the document said.

“We mean specifically attempting to escalate the tension between America and Iran, and American and the Shiite in Iraq,” it quoted the documents as saying, especially among moderate followers of Grand Ayatollah Ali al-Sistani, the most influential Shiite cleric in Iraq.

The document’s authenticity could not be independently verified.

National Security Adviser Mouwafak al-Rubaie called it “the beginning of the end of al-Qaida in Iraq.”

“Now we have the upper hand,” he said at a news conference in Baghdad. “We feel that we know their locations, the names of their leaders, their whereabouts, their movements, through the documents we found during the last few days.”

Baghdad was in the second day of a huge security crackdown involving 75,000 Iraqi army and police forces backed by U.S. forces. It includes a curfew extended by 4 1/2 hours _ from 8:30 p.m. until dawn _ a weapons ban, and the frisking of motorists at checkpoints around the capital. The government did not say how long the crackdown would last.

Operation Forward Together began Wednesday _ one day after Bush visited Baghdad to reassure Iraqis of Washington’s continued support and exactly a week after al-Zarqawi’s death in a U.S. airstrike.

Prime Minister Nouri al-Maliki has promised the crackdown would not target any ethnic or sectarian group.

Gunmen killed an engineer and kidnapped another, and a detergent factory worker was shot to death as he was headed to work elsewhere in western Baghdad, police said, but no major violence was reported in the capital, a day after al-Maliki’s major security operation was launched.

Elsewhere, however, gunmen stormed a Sunni mosque near Tikrit, killing four people and wounding 15, including a fundamentalist Sunni cleric who has spoken out against the killing of Iraqis as part of the insurgency.

Al-Maliki opened the door Wednesday for talks with insurgents opposed to the country’s political process as part of a national reconciliation initiative, but he said any negotiations would exclude terrorist groups. The plan could include a pardon for some prisoners.

Deputy Justice Minister Busho Ibrahim said 421 Iraqi prisoners were released from U.S. detetntion centers in Iraq on Thursday, the latest batch of a total of 2,500 to be freed this month as part of al-Maliki’s national reconciliation efforts.