A female suicide b****er struck Shi'ite worshippers in the holy city of Karbala on Monday, an official and a witness said, killing at least 43 people and leaving pools of *lo** 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 US soldiers also were killed Monday in a roadside b****ing north of Baghdad, bringing the American death toll closer to 4,000 as the US-led war enters its sixth year. At least 3,990 members of the US military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Condemned attack

The violence marred overlapping trips by Vice-president Dick Cheney and Senator 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 American Embassy and the military issued a joint statement condemning the "barbaric attack" and blaming it on al-Qaida in Iraq.

The Karbala attack came after the worshippers had gathered at a sacred historical site about a kilometre (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 authorised to release the information, said the attacker was a woman - as did a witness.