There were no reports of US casualties in the 90-minute attack on Monday, the second in the past 10 days against the government headquarters for Anbar province, a centre of the Sunni Arab-dominated revolt against the current Iraqi government.
In Baghdad, US and Iraqi forces fought an hours-hour gun battle with about 50 fighters in the Sunni Arab district of Adhamiyah, the US military said. Five fighters were killed and two Iraqi soldiers were wounded, the US said.
The latest attack here began when two suicide car bombers sped towards the government building, known in Baghdad as Government Centre, using a road closed to civilian traffic, marine Captain Andrew Del Gaudio said.
US marines fired flares to warn the vehicles to stop and 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 US post, Del Gaudio said.
Mortars and grenades
As part of the assault, other fighters fired mortars and rocket-propelled grenades at marine positions at the roof of the Government Centre, which includes the office of the Anbar governor, and at a another observation post, Del Gaudio said.
A US army tank fired a 120 mm shell at a small white mosque from where about 15 fighters were shooting at the Government Centre, Del Gaudio said. The round damaged part of the minaret and the firing ceased, he said.
Lieutenant-Colonel Stephen M. Neary, commander of the 3rd Battalion, 8th Marine Regiment, said it was the fourth time in the past three and a half weeks that fighters had used the mosque to fire on the government building.
Iraqi army soldiers are battling
Sunni fighters on a daily basis
The total number of casualties among the anti-government fighters was unknown. But Lieutenant Carlos Goetz said marines killed at least three of them who were firing mortar rounds towards the Government Centre.
In Baghdad, fighting erupted in Adhamiyah before dawn when an Iraqi army patrol came under fire, a US statement said.
Four hours later, a US-Iraqi checkpoint in the area was attacked by armed men, prompting the command to send American and Iraqi reinforcements. The US statement said clashes continued until early afternoon.
The attack in Ramadi was the biggest since April 8, when fighters besieged the Government Centre until US jets blasted several buildings used by armed men to fire on the marines.
Before the upswing in violence, US officials had been encouraged by a relative lull in Anbar, suggesting that it was due to weariness among ordinary Sunni Arabs who were turning against al-Qaeda-led anti-government groups.
Another 17 bodies of people believed to be victims of sectarian reprisal killings were found on Monday, including one in Basra and the rest in Baghdad.
They included the body of Taha al-Mutlaq, brother of leading Sunni Arab politician Saleh al-Mutlaq, who was found in a Shia area of west Baghdad.
Sunni politician Saleh al-Mutlaq's
brother Taha was found dead
Taha al-Mutlaq disappeared last month en route to Salahuddin province north of Baghdad, and Saleh al-Mutlaq speculated that he had been kidnapped because of his political activity.
Elsewhere on Monday, bombs killed one civilian in Baghdad and another in Baquba, and a bricklayer was slain in Kirkuk after his family could not pay a ransom demand, police reported.
In other incidents, a Shia cleric was killed on Monday night in southwest Baghdad during a drive-by shooting, police said.
The formation of a national unity government of Shias, Sunnis and Kurds has stalled due to Sunni and Kurdish objections to the Shia candidate to head the new government, Ibrahim al-Jaafari, the prime minister.
Prospects for a quick end to the stalemate were in doubt on Tuesday 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 that he won in a Shia caucus last February.
Parliament had been set to meet on Monday to try to break the deadlock, but the session was postponed after Shia politicians gave assurances they could reach a decision on al-Jaafari themselves without a bruising parliamentary fight.
Bombs killed civilians in Baquba
and Baghdad on Monday
One option floated called for replacing al-Jaafari with another candidate from Dawa, one of the seven parties in the Shia alliance.
But Ali al-Adeeb, a top Dawa official whose name has been mentioned as a possible replacement, said on Monday that the party would not put forward a new candidate unless al-Jaafari decided to step aside, suggesting further delays.