BAGHDAD - Police and hospital officials say an explosion at an iron factory on the outskirts of a northern Iraqi city has killed five workers and wounded 15. Police Chief Abdul-Khaliq Talaat said the cause of the Sunday explosion just outside the city of Irbil was not immediately known. Irbil is located in Iraq's self-rule Kurdish region about 217 miles (350 kilometres) north of Baghdad. An Irbil hospital worker confirmed the deaths. An al-Qaeda front group in Iraq declared in a statement posted on the Internet Sunday that its two top figures have been killed. The statement by the Islamic State of Iraq provided the first confirmation from the terror network of the April 19 claim by the Iraqi and US governments that the two men were killed in a joint operation while hiding at a safe house near the city of Tikrit, north of Baghdad.