Ten US marines have been killed in a bomb explosion in the Iraqi city of Falluja. It comes amid an operation against insurgents by American and Iraqi forces in the neighboring town of Ramadi where rebels recently staged a show of strength. Another 11 soldiers were wounded in the blast, which was caused by what the US military described as an “improvised device”.Insurgents attacked a military base in Ramadi with rockets and mortars on Thursday. They then distributed leaflets saying Al Qaeda in Iraq was in control of the town, before dispersing several hours later. The US denies the insurgents did over-run Ramadi, which is in the heartland of Iraq’s Sunni-led revolt. Many insurgents are believed to have infiltrated the area after US forces drove them out of their base in Falluja in November last year. Despite the recent activity the area appears to have returned to relative calm. US and Iraqi authorities are trying to clamp down on the rebels ahead of a parliamentary election on December 15.