As many as 20 people were killed on Saturday in suicide car bomb attacks in Iraq with dozens of others wounded amid US claim of the arrest of a senior aide to Washington's top foe, Abu Musab al-Zarqawi.

Sixteen people were killed and 40 others wounded in a suicide car bomb attack on a police recruitment center at a US-Iraqi base in western Iraq.

The morning attack occurred at the Baghdadi base, about 200 km west of Baghdad, which is used by US forces and the Iraqi NationalGuards, when a suicide bomber blew himself up after he drove an explosive-laden vehicle near the police academy outside the gate, police said.

Another suicide car bomb exploded near a checkpoint controlled by the Iraqi National Guards north of Baghdad, killing four guardsand wounding six others.

The US military had no immediate information on the blasts. Iraqi police and security forces have been targets since the US-led invasion of Iraq last year.

Meanwhile, six US soldiers were injured when their armored vehicle was hit by a roadside bomb on a highway leading to Baghdadairport, said the US military, adding none of the soldiers received life-threatening injuries.

Also on Saturday, the US military said it has arrested a seniormember of the Islamic militant group run by Abu Musab al-Zarqawi in overnight raids in Iraq's Fallujah city.

"Due to a surge in the number of Zarqawi associates who have been captured or killed by multinational strikes and other operations, the member had moved up to take a critical position asa Zarqawi senior leader," the US military said in a statement.

During the raids that were launched in the early morning by theUS forces, five other Zarqawi followers were also nabbed, the statement added.

The US forces have recently stepped up operations in Fallujah, 65 km west of Baghdad, in an effort to root out anti-US militants,who are said to be behind suicide bombings and beheadings of foreign hostages.

A militant group in Iraq, the Army of Ansar al-Sunna, said on its website on Saturday it has beheaded an Iraqi man accused of collaborating with US forces.

The man was beheaded after "confessing to all the actions he carried out," said the statement on the web, adding he worked at a US base in Mosul airport and "was known for his allegiance to the Americans and his hatred for the mujahedeen (Islamic fighters)."