Yesterday, suspected insurgents opened fire on a convoy carrying Iraq's oil minister, killing two of his bodyguards, police said.

Ibrahim Bahr was not hurt in the attack, which occurred at 9:30 a.m. in western Baghdad, said police Lt. Mohammed Kheyon. A third bodyguard was wounded.

Meanwhile, al-Qaeda in Iraq claimed to have taken two Marines captive during the fighting and threatened to kill them within 24 hours unless all female Sunni detainees are released from US and Iraqi prisons in the country. The US military said the claim appeared false.

"There are no indications that the al-Qaeda claims ... are true," Multinational Force West, the command in the region said. It said it was conducting checks "to verify that all Marines are accounted for."

Even as the fighting continued, political differences among Iraqi leaders deepened ahead of the crucial Oct. 15 national vote on a new constitution. Iraq's Kurdish president, Jalal Talabani, called on the Shia prime minister to step down over accusations he is monopolizing power in the government and ignoring his Kurdish coalition partners' demands, a spokesman for Talabani's Patriotic Union of Kurdistan said.

The US military says al-Qaeda in Iraq, the country's most fearsome insurgent group, has turned the area near the border into a "sanctuary" and a way-station for foreign fighters entering from Syria.

In Karabilah, Marines clashed with insurgents who opened fire from a building on Sunday in a firefight that killed eight militants, the military said.

The move into Karabilah widened the sweep launched a day earlier by 1,000 Marines, soldiers and sailors, starting with nearby Sadah a tiny village about eight miles from the Syrian border.