Iraq's interim prime minister, Ayad Allawi, on Tuesday accused foreign troops in the country of "gross negligence" in the massacre of 49 Iraqi National Guard recruits over the weekend, an unusually critical remark by the U.S.-backed leader.

Allawi, in a weekly address to the Iraqi National Assembly, said his government had launched an investigation into the deaths of the U.S.-trained recruits, most of whom were lined up and executed shortly after sunset Saturday near the National Guard's main training base in Kirkush, about 60 miles northeast of the capital.

"A terrible crime was committed in which a large number of the ING were martyred," Allawi said. "We think this shows, in addition to gross negligence on the side of some of the multinational forces, it shows the kind of insistence to hurt Iraq and its people."

Allawi, whose interim administration assumed political authority from the U.S.-led occupation authority in late June, did not explain how foreign forces had been negligent. Efforts to reach government spokesmen on Tuesday night were unsuccessful.

The remark was an unusual public condemnation of the U.S. military and its allies in Iraq from the prime minister, who worked closely with Washington as an exile leader during the rule of President Saddam Hussein. His political party, the Iraqi National Accord, was funded for several years by the CIA.

The unarmed recruits killed Saturday had just left the Kirkush training base aboard three buses when they were stopped at a checkpoint manned by insurgents dressed as Iraqi police officers, according to Iraqi officials. The recruits appeared to have been forced off the buses, lined up, ordered to lie facedown and then shot. The buses, which were taking the recruits from the base for the start of a 20-day leave, were not accompanied by security vehicles.

In a statement on Tuesday, the U.S. military called the killings "a cold-blooded and systematic move by terrorists" and said U.S.-led forces were not responsible.

The terrorists "and no one else must be held fully accountable for these attacks," the statement said. The Iraqi interim government "is investigating this tragic incident. Multinational forces will fully support and cooperate to establish the facts and avoid repetition of similar events."

In Washington, a former top occupation security official said more Iraqis were being trained for the country's security forces than the United States and its allies are capable of protecting.

"There are so many being trained now, U.S. forces can't watch them all now," said Peter Khalil, an Australian defense expert who was in Iraq from last summer until this spring as the director of national security policy for the Coalition Provisional Authority. "There are 40 battalions of the Iraqi National Guard, six or seven battalions of the Iraqi army. Recruits are coming in all the time. You don't have force levels to protect indigenous forces."

Insurgents in recent months have carried out frequent attacks on Iraqi security forces and recruits, who are being trained to eventually assume responsibility for security in the country. There are about 100,000 members of the Iraqi security forces, and that number is expected to increase to 145,000 by January and 250,000 by the end of next year, according to U.S. and Iraqi officials.

Meanwhile, an insurgent group, the Ansar al-Sunna Army, said Tuesday that it had kidnapped 11 Iraqi National Guardsmen, according to a statement posted on its Web site, the Reuters news agency reported.

"The mujaheddin in the army of Ansar al-Sunna captured a group of militia linked to the coalition forces that was out on patrol along the Baghdad-to-Hilla road," the group said in the statement. Hilla is about 60 miles south of Baghdad.

The claim could not immediately be verified, but a video and photographs of the men and their captors was posted on the site.

In a separate development, a militant Islamic Web site posted a video of what it claimed was a Japanese man kidnapped by insurgents loyal to Abu Musab Zarqawi, a Jordanian-born militant whose organization asserted responsibility for Saturday's massacre, the Associated Press reported. The Web site said the man would be beheaded within 48 hours unless Japan withdraws its troops from Iraq. Japanese Prime Minister Junichiro Koizumi rejected the demand.

In the insurgent-held city of Fallujah, the U.S. military said it had killed an associate of Zarqawi. The military said multiple sources reported that the associate was in a house in northwest Fallujah when it was attacked by U.S. aircraft at 3 a.m. on Tuesday.

The U.S. government, which has accused Zarqawi of engineering many of the deadliest attacks in Iraq in recent months, has offered a $25 million reward for his capture or death. Military forces have struck Fallujah, where they believe Zarqawi and his operatives are based, almost nightly for the past several weeks. A major offensive there is expected, possibly after the U.S. presidential election, and most of the city's residents have fled in anticipation.

Allawi predicted on Tuesday that insurgent attacks would increase and become even more violent. "The enemies know if Iraqi stabilizes, it will be a serious defeat to them," he said. "Thus, they'll escalate the situation. You should expect wider operations than ones done now against Iraq."

But Allawi vowed the insurgents would ultimately lose.

"I am confident that the majority of Iraqis are willing to cooperate to stabilize the country," he said.

Special correspondent Omar Fekeiki in Baghdad and staff writer Thomas E. Ricks in Washington contributed to this report.

Ayad Allawi, Iraq's interim prime minister, led a CIA-funded exile group for several years.