The U.S. military on Friday announced the deaths of six more American troops killed in the recent barrage of violence that has swept Iraq, bringing to 11 the number of troops slain on the same day.

A U.S. Marine and soldier died in the attack by a homicide bomber who infiltrated a line of police recruits in Ramadi on Thursday, killing at least 58 and wounding dozens. Two soldiers were also killed in the Baghdad area when their vehicle hit a roadside bomb, the military said Friday.

In addition, two U.S. Marines were killed by separate small arms attacks while conducting combat operations in Fallujah, the military said.

The military had previously announced the deaths of five soldiers hit by a roadside bomb south of Karbala. The attack came minutes before a second homicide bomber struck Shiite pilgrims in that city, killing 63.

It was the fourth-deadliest day in Iraq since the fall of Saddam Hussein in 2003, with at least 136 total deaths, including the U.S. troops.

The 11 U.S. deaths were the most in a single day since 11 Americans were killed on Dec. 1. On that day, 10 Marines were killed by buried bombs as they gathered for a promotion ceremony in an abandoned flour mill in Fallujah, and one soldier was killed in Ramadi.

At least 2,194 members of the U.S. military have died since the war began, according to an Associated Press count.

Ball bearings from the suicide attacker's vest lay scattered on the earth next to Shiite Islam's holiest shrine in Iraq after the Karbala attack.

In Ramadi, a Sunni insurgent stronghold 70 miles west of the capital, Marine Capt. Jeffrey S. Pool said police recruits got back in line to continue the screening process after a homicide bomber attacked. They were apparently desperate for a relatively well-paying job in the impoverished area.

Prime Minister Ibrahim al-Jaafari, a Shiite, denounced the violence as an attempt to derail the political process at a time when progress was being made toward a broad-based government that would include the Sunni Arabs and thus possibly weaken the insurgency.

Iraq's main Shiite religious party, the Supreme Council for the Islamic Revolution, issued a veiled threat to Sunnis supporting the insurgency that its patience was wearing thin.

But in a chord struck by several politicians, the party also condemned policies it said were imposed by the U.S.-led coalition that were hampering Iraqi security forces' counterterrorism work. The Americans have increased their oversight of Shiite-dominated security forces following widespread charges of abuse, especially of Sunni Arab detainees.

"Not allowing these two ministries to do their job means exposing helpless Iraqis to ruthless terrorists," SCIRI said. "They should know that the patience of our people will not last for a long time with these sectarian dirty crimes."

The warning to Sunnis carried the possibility of using militias like the Badr Brigade, the former military wing of SCIRI, to exact vengeance against Sunni supporters of insurgents.

Hadi al-A'meri, the secretary general of the Badr Brigade, also blamed the attacks on the U.S.-led coalition.

"Why are they putting obstacles in the way of the work of the Interior Ministry?" he asked.

The U.S. Embassy in Baghdad said it was appalled by the attacks.

"This terror aims simply to kill innocent Iraqis and provoke further conflict between them," the embassy said.

The Iraqi Accordance Front, the main Sunni coalition that is negotiating with Shiites and Kurds over a coalition government after the Dec. 15 election, denounced the violence but blamed Iraq's leaders for allowing it to happen.

"This government ... has become an accomplice in the cycle of violence by adopting sectarian policies and by weakening the state and strengthening militia groups," said Izzat al-Shahbandar, a senior official with the Sunni coalition.

The three main attacks Thursday all took place within an hour. The death toll was the largest single-day total since Sept. 14, when 162 died.

Mohammed Saheb, who was wounded in the head in the Karbala attack, said he travels to the shrine every Thursday in advance of Friday prayers — as many pilgrims do.

"I never thought that such a crime could happen near this holy site," Saheb said. "The terrorists spare no place from their ugly deeds."

The Karbala bomber detonated a vest stuffed with about 18 pounds of explosives and several hand grenades, Col. Razaq al-Taie said.

The bombing brought back memories of the deadliest civilian attack in Iraq since the war began. On March 2, 2004, coordinated blasts from suicide bombers, mortars and planted explosives exploded near shrines in Karbala and Baghdad, killing at least 181 people. Since then, however, Karbala had been relatively free of violence.

Karbala Gov. Aqeel al-Khazraji blamed "takfiris and Saddamists" for the attack. The takfiri ideology is followed by extremist Sunnis bent on killing anyone they consider an infidel, even fellow Muslims.

The attack in Ramadi came 40 minutes later, when a bomber standing among some 1,000 police recruits struck near the Ramadi Glass and Ceramics Works. Mohammed al-Ani, a doctor at Ramadi General Hospital, said 56 people were killed and 60 wounded.

In other violence Thursday, a homicide car bomb killed three Iraqi soldiers in Baghdad, Lt. Col. Thamir al-Gharawi said, and gunmen killed three people in separate incidents, police said, raising Thursday's toll to 136.

On Wednesday, 53 people died in attacks, including 32 killed by a suicide bomber at a Shiite funeral.