BAGHDAD, (AP) – A suicide bomber blew himself up Tuesday among dozens of Iraqi army recruits who had gathered near a military headquarters in downtown Baghdad in a devastating strike that officials said killed 51 people and wounded 119.

The massive morning blast took place just outside the former Iraqi Ministry of Defense building that now houses the army’s 11th division headquarters. The site receives about 250 new recruits each week as Iraqi security forces try to bolster their ranks to prepare for the U.S. military’s looming withdrawal after seven years of war.

Blown-off hands and legs could be seen among pools of blood at the scene, which Iraqi soldiers closed off. U.S. helicopters hovered overhead as frantic Iraqis showed up to search for relatives.

The recruits were gathered in an open area next to Maidan Square in central Baghdad as they waited to be let through the main gates in small groups, according to two Iraqi police officials who spoke on condition of anonymity. At least three soldiers were among the dead and eight among the wounded, the police officials said.

Officials at four Baghdad hospitals confirmed the casualties.

The officials spoke on condition of anonymity because they were not authorized to talk to the media.

Iraqi security forces have been trying to boost their numbers as the U.S. military begins to leave the country. All but 50,000 U.S. troops will go home by the end of August, with the rest to follow by the end of 2011 under a security agreement between Baghdad and Washington.

But insurgents determined to highlight the Iraqi government’s struggle to protect the nation have been stepping up attacks in recent weeks.

Iraqi army, police and other security forces have been targeted, but civilians also have been killed by the hundreds.