QAIM, Iraq - A U.S. offensive aimed at al-Qaida in Iraq insurgents in western Iraq entered its third day today, with airstrikes in a town on the banks of the Euphrates River, witnesses said. At least 36 militants have died since the fighting began, officials said.

No serious U.S. casualties have been reported in the "Iron Fist" offensive by 1,000 Marines, soldiers and sailors near the Syrian border.

In Baghdad, Iraq's oil minister narrowly survived an assassination attempt when a roadside bomb blasted his seven-car convoy, killing three of his escorts, officials said.

Elsewhere, roadside bombs and fighting between insurgents and Iraqi forces today wounded at least seven Iraqis in Ramadi, a militant stronghold 70 miles west of the capital, officials said.

Insurgents wearing black hoods were seen carrying machine guns and rocket-propelled grenades in the city's streets, and Iraqi civilians gathered around two burning Iraqi army pickup trucks. Some of the civilians celebrated the destruction by carrying Iraqi military helmets and a uniform that appeared to have been pulled from the burning Iraqi vehicles.

In the northern city of Mosul, a drive-by shooting killed Nafi'a Aziz, a female member of Ninevah's provincial council, and her son, said police spokesman Brig. Saeed Ahmed. Aziz was in charge of the council's human rights committee and a member of the Patriotic Union of Kurdistan, the party of Iraqi President Jalal Talabani.

Mosul is 225 miles northwest of Baghdad.

The offensive and street fighting come less than two weeks before the national referendum on a new Iraqi constitution. Al-Qaida in Iraq and other groups in the Sunni-led insurgency have killed at least 207 people over the past eight days in a bid to wreck the vote.

On Sunday, Al-Qaida in Iraq claimed to have taken two U.S. Marines captive during the fighting and threatened to kill them within 24 hours unless all female Sunni detainees are released from U.S. and Iraqi prisons in the country. The U.S. military said the claim appeared false but that it was conducting checks "to verify that all Marines are accounted for."

Coalition forces today announced the arrest late last week of 12 Iraqis suspected of being involved in an illegal local committee that punishes violators of Islamic law in Sadr City, a section of Baghdad partially controlled by radical Shiite cleric Moqtada al-Sadr.

Al-Sadr's militia, the al-Mahdi Army, was a stubborn problem for American forces until a truce was negotiated about a year ago.

The U.S. offensive in western Iraq by 1,000 Marines, soldiers and sailors began early Saturday in the village of Sadah and has since spread to Karabilah and Rumana, two nearby towns on the banks of the Euphrates River. Witnesses told The Associated Press today that helicopter attacks on Rumana were sending up clouds of black smoke.

No casualties were reported in today's fighting by the witnesses, who spoke on condition of anonymity out of concern for their own safety, or by the U.S. military command center in Baghdad.

The military says al-Qaida in Iraq, the country's most feared insurgent group, has turned the area near Iraq's 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.

Most of the militants appeared to have slipped out of Sadah before the force moved in, and hundreds of the village's residents fled into Syria ahead of the assault.

There was "virtually no opposition" in Sadah, the Marine commander in western Anbar province, said Col. Stephen Davis.

At least 28 militants were killed in fighting Sunday, Davis said, bringing the two-day toll among insurgents to 36.