At least 10 people have been killed and several others have been injured after a bomb exploded at a US-Iraqi base near Ramadi, in the West of Iraq.The US military said there are no American casualties. The base is used as a centre to recruit Iraqi police. Shortly afterwards, four Iraqi national guards were killed in a suicide attack in Samarra, north of the capital. In Baghdad, two civilians were killed when insurgents fired mortar rounds into a commercial district. One other person was wounded. Meanwhile, the US military says it has captured a close aide of its most wanted man in Iraq, Jordanian militant Abu Musab al-Zarqawi, in a series of raids on the rebel held city of Falluja. Al Zarqawi, who in the past has pledged his allegiance to Osama bin Laden, has claimed responsibility for a series of kidnappings and suicide bombings in Iraq. Two people were killed in the raids and three other suspected militants captured.