The two-day death toll from insurgent attacks rose to 163, a surge of violence not seen since before the Dec. 15 parliamentary elections. Attackers killed 53 people on Wednesday.
A statement from the U.S. military said only that the soldiers were patrolling in the Baghdad area, while Iraqi police Capt. Rahim Slaho said a U.S. convoy headed for the Shiite holy city of Karbala had been attacked 15 miles south of the city and that five soldiers were killed. No names were released.
The suicide blast Thursday near the Imam Hussein shrine in central Karbala, 50 miles south of Baghdad, killed 49 people and injured 52, Karbala police Col. Razaq al-Taie.
In the attack's aftermath, a woman and an infant girl in a bright red jumpsuit lay in a pool of blood, their faces covered by a sheet. Television images showed men ferrying the wounded in pushcarts. The bomber appeared to have set off the explosion only about 30 yards from the shrine in a busy pedestrian area surrounded by shops.
In Ramadi, a U.S. spokesman said about 30 people were killed when a suicide bomber attacked a line of about 1,000 police recruits. Iraqi police said about 40 people were injured.
The attack took place at a police screening center in Ramadi, an insurgent stronghold 70 miles west of Baghdad. Marine Capt. Jeffrey S. Pool said recruits later got back in line to continue the screening process.
In other developments:
The Karbala bomber detonated a vest with about 17.5 pounds of explosives and several hand grenades, al-Taie said. Small steel balls that had been packed into the suicide vest were found at the site, as was one unexploded grenade, he said.
Many pilgrims travel to Karbala on Thursdays to be at the holy site for Friday prayers. One pilgrim, Mohammed Saheb, said he travels to Karbala every Thursday.
"I never thought that such a crime could happen near this holy site," said Saheb, who sustained a head injury. "The terrorists spare no place from their ugly deeds. This is a criminal act against faithful pilgrims. The terrorists are targeting the Shiites."
Speaking from a hospital bed where he was being treated for burns and bruises, Akram Saleh, a vendor, said he lost consciousness after the explosion.
"I was selling toys near the shrine when I flew into the air because of the explosion," he said.