Ramadi, Iraq ? U.S. troops repelled an attack Monday by Sunni Arab insurgents who used suicide car bombs, rocket-propelled grenades and automatic weapons in a coordinated assault against this city’s main government building and two U.S. observation posts.

The fighting in Ramadi, the capital of Anbar province, provided fresh evidence that the insurgency is thriving in Sunni Arab-dominated areas despite last month’s decline in U.S. deaths.

In Baghdad, U.S. and Iraqi forces fought an hourslong gunbattle with about 50 insurgents in the Sunni Arab district of Azamiyah, the U.S. military said. Five insurgents were killed and two Iraqi troops were wounded, the U.S. said.

There were no reports of U.S. casualties in the 90-minute attack in Ramadi, the second in the past 10 days against the government headquarters for Anbar.

The latest attack began when two suicide car bombers sped toward the government building, known here as Government Center, using a road closed to civilian traffic, Marine Capt. Andrew Del Gaudio said.

U.S. Marines fired flares to warn the vehicles to stop. When they refused, the Americans opened fire with .50 caliber machine guns from the building’s sandbagged rooftop. The vehicles turned and sped away but exploded on a main road, sending a huge fireball into the sky and triggering a shock wave that damaged the U.S. post, Del Gaudio said.

As part of the assault, other insurgents fired mortars and rocket-propelled grenades at Marine positions at the roof of the Government Center, which includes the office of the Anbar governor, and at another observation post, Del Gaudio said.

A U.S. Army tank fired a 120 mm shell at a small white mosque where about 15 insurgents were shooting at the Government Center, Del Gaudio said. The round damaged part of the minaret and the firing ceased, he said.

Lt. Col. Stephen M. Neary, commander of the 3rd Battalion, 8th Marine Regiment, said it was the fourth time in the past 3 1/2 weeks that insurgents had used the mosque to fire on the government building.

In order to quell unrest across the country, U.S. officials have been urging the Iraqis to speed up formation of a national unity government of Shiites, Sunnis and Kurds. The process has stalled because of Sunni and Kurdish objections to the Shiite candidate to head the new government, Prime Minister Ibrahim al-Jaafari.

Prospects for a quick end to the stalemate were in doubt Monday as al-Jaafari’s Dawa party pledged to support him for another term as long as he wants the job. Al-Jaafari has refused to give up the nomination, which he won in a Shiite caucus last February.