BAGHDAD,(Reuters) – A U.S. air raid in Baghdad on Friday killed at least eight people, medical sources said, while the Iraqi army said it had killed 30 suspected al Qaeda insurgents north of the capital.

A medical source at Yarmouk Hospital in Baghdad said eight bodies had been brought in from a southern neighbourhood after U.S. helicopters targeted a building. A police source put the toll at 10, saying many were believed to be civilians. The U.S. military had no immediate comment.

It is the second time this week that U.S. forces have been accused of killing civilians in air strikes. U.S. forces are investigating an attack in southern Iraq this week which local police said killed five women and four children.

In Washington, a military spokeswoman said the first U.S. military unit scheduled to withdraw from Iraq under President George W. Bush’s plan to cut troop levels had left the war zone. The 13th Marine Expeditionary Unit, a group of 2,200 Marines who were stationed in western Anbar province, had boarded a naval vessel and begun its trip home.

Bush ordered the reductions, approving a plan from his top commander in Iraq to bring U.S. force down by about 20,000 to 30,000 by mid-2008.

The president has said his policy of sending extra troops to Iraq to curb violence and give the country’s feuding Sunni Arab, Shi’ite and Kurdish politicians a chance to start burying their differences has been working. But there have been calls this week in Washington for more power to be given to Iraq’s regions. The U.S. Senate passed a resolution on Wednesday calling for separate Sunni, Shi’ite and Kurdish federal regions.

Returning from the United Nations General Assembly, Iraqi Prime Minister Nuri al-Maliki on Friday rejected the proposal saying it would be a disaster for Iraq. “They should stand by Iraq to solidify its unity and its sovereignty,” Maliki told state television on his flight back. “They shouldn’t be proposing its division. That could be a disaster not just for Iraq but for the region.”

On Monday a suicide bomber killed 26 people in a mosque compound in Baquba where local Shi’ite and Sunni Arab leaders were holding reconciliation talks. Two days later bombings across the country killed more than 50 people.

The attacks fuelled U.S. concerns that Sunni al Qaeda militants in Iraq are ramping up a campaign of violence to coincide with the Muslim holy month of Ramadan.

An Iraqi army officer said on Friday the 30 suspected al Qaeda insurgents were killed during a raid on a village southwest of Baquba, 65 km (40 miles) north of Baghdad.

Bush faces domestic pressure to start bringing more troops home from a war in which 3,800 U.S. soldiers have died.

U.S. army officers say their stepped-up security drive around Baghdad is yielding results and led to a decline in the number of U.S. troop casualties so far this month.

Fifty-nine U.S. soldiers have been killed in September, according to the Web site icasualties.org which tracks military deaths, making it the least deadly month for U.S. troops since July last year. Twenty-two of the deaths were defined as “non-hostile”, many of them road accidents. “What we found is that the current operations … managed to disrupt a lot of (militant) cells,” said a U.S. military spokesman, Lieutenant-Colonel Rudy Burwell. “We were able to push them from Baghdad and pursue them”. “That’s what we attribute the lower casualties to.” “Obviously (the militants) have not been eliminated, but they have been disrupted,” he said, adding shooting attacks and roadside bombs had been “trending downwards” since June.

September’s figure is on track to be about half the death toll for May, when extra U.S. forces deployed in greater strength into dangerous areas, in what was seen as a last ditch attempt to reduce Iraq’s sectarian fighting.