BAGHDAD -- A female suicide bomber struck Shiite worshippers in the holy city of Karbala on Monday, an official and a witness said, killing at least 43 people and leaving pools of blood on the street leading to one of Iraq's most revered mosques.
The blast was the deadliest in a series of attacks that left at least 72 Iraqis dead, including six youths killed when mortar rounds slammed into a soccer field in eastern Baghdad.
Two U.S. soldiers also were killed Monday in a roadside bombing north of Baghdad, bringing the American death toll closer to 4,000 as the U.S.-led war enters its sixth year. At least 3,990 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.
The violence marred overlapping trips by Vice President Dick Cheney and Sen. John McCain to Baghdad. Their visits were aimed at touting recent security gains and stressing Washington's long-term commitment to fighting insurgents in Iraq.
The Karbala attack came after the worshippers had gathered at a sacred historical site about half a mile from the golden domed shrine of Imam Hussein, a grandson of the Prophet Muhammad who was killed in a seventh-century battle.
A police officer, speaking on condition of anonymity because he wasn't authorized to release the information, said the attacker was a woman -- as did a witness.
The U.S. military described the attack as a suicide operation but put the casualty toll at 40 Iraqis killed and 65 wounded. The U.S. statement said the identity of the bomber remained unknown.
Brig. Gen. Raed Shakir Jawdat, Karbala's police chief, said 43 people were killed and 73 wounded. He denied it was a suicide attack, saying a bomb had been planted in the area. The discrepancies could not immediately be resolved.
Karim Khazim, the city's chief health official, said seven of those killed were Iranian pilgrims who had traveled to the holy site.
AP Television News footage showed a man carefully picking up pieces of flesh and wires apparently from a fuse as evening prayer services were broadcast from loudspeakers nearby.
The witness, who did not identify himself, told AP Television News that a woman in the crowd had blown herself up.
If true, it would be among the deadliest attacks carried out by women during the Iraq conflict.
Female suicide bombers have been involved in at least 20 attacks or attempted attacks since the war began, including the grisly bombings of two pet markets in Baghdad that killed nearly 100 people last month.
The U.S. military has warned that insurgents are using female attackers because they can more easily avoid checkpoint searches and can hide the explosives under traditional all-encompassing black Islamic robes.