An Iraqi Interior Ministry official said the explosion occurred on Monday at an Iraqi army centre called Tamarat, located near the town of Tal Afar, which is close to the  restive city of Mosul. "Forty people have died and 20 were wounded when a suicide  bomber blew himself up in the midst of candidates waiting at a  recruitment centre for Iraq defence forces," the official said.

Earlier, an official with the Nineveh governorate of which Mosul is the capital had also confirmed that the attack was carried out by a suicide bomber. The US military said there were no American casualties.
  
The latest attack is one of the bloodiest in the last four months after the November suicide bombing on a police recruitment centre in Ramadi which left 70 dead.

Aljazeera