At least 14 people were killed and 20 wounded in an apparent suicide bomb attack on Iraq's Interior Ministry on Monday as the country marked National Police Day, police said. Police said that they believed two suicide bombers detonated explosives outside the building in eastern Baghdad. They were trying to establish how one of the bombers had managed to get through a series of checkpoints in the heavily guarded compound. A ceremony celebrating the 84th anniversary of the formation of the Iraqi police force was taking place at the police academy next door to the ministry at the time of the blast. Among the dignitaries attending were the U.S. ambassador, Zalmay Khalilzad, and the Iraqi defense and interior ministers. U.S. military spokesman Lieutenant-Colonel Barry Johnson, who was at the ceremony, denied an Iraqi state television report that a mortar bomb had hit the parade ground. "The blast could be heard in the distance, but no mortar hit the parade ground," he told Reuters.