A bomber wearing a belt of explosives detonated within 50 feet of a police station, inside the station's security perimeter, Britain's Daily Telegraph reported.
According to U.S. and Iraqi officials, at least 22 people were killed and nearly 30 wounded while they were waiting in line to apply to be army officers at the station.
"To attack and brutally murder patriotic and innocent Iraqis on their way to volunteer to protect their homeland is a crime against all people of Iraq," Thair al-Nakib, a spokesman for interim Iraqi Prime Minister Iyad Allawi, said in a statement, reported the Associated Press.
The attack is the third in two days, following dual blasts in the cities of Mosul and Baquba Monday that killed at least 35 people. More than 20 people were killed in Mosul when a suicide bomber lured a group of Iraqi policemen into a trap, according to Reuters. In Baquba, an explosive-laden taxi blew up alongside potential police recruits, killing at least 15.
Iraq's al-Qaida network, led by Jordanian Abu Musab al-Zarqawi, has claimed responsibility for all three attacks in a statement posted on an Islamist Web site. "Here come the convoys of martyrs to strike the headquarters of infidels and apostates, and this is the beginning of the escalation we had promised," Reuters reported.
U.S. officials said Tuesday's attack targeted a truck carrying recruits into the base in a disused airport in Baghdad.
The recent insurgent attacks have focused on Iraq's security forces in attempts to disrupt efforts to stabilize the country after Jan. 30 elections. The U.S. military says it needs more time to train Iraqi forces.