A homicide bomber with explosives hidden beneath his traditional robe blew himself up Tuesday in a crowd of Iraqis trying to join the police force, killing at least 25 people in Iraq's second major bombing this week.

The attack occurred in the town of Jalula, a remote, impoverished community in Diyala province about 80 miles northeast of Baghdad.

Initial reports from police and the U.S. military said the bomber detonated an explosives-laden vehicle near a building where would-be recruits for a new police emergency response unit had assembled.

Later, however, the Diyala Operations Center and the Jalula police said the bomber mingled in the crowd and then detonated explosives hidden beneath his traditional dishdasha robe. The explosives were packed with nails and ball-bearings to maximize casualties, police said.

He detonated the explosives near a parked car, leading police to conclude the attacker used a car bomb, police said.

U.S. military officials said five policemen were among the dead.

Police guard Falah Hassan, 28, said he was standing at the gate of the Jalula police compound when he heard a thunderous explosion go off about 100 yards away.

"I saw burned bodies, wounded people and small pools of blood," said Hassan, speaking from a hospital bed in the northern town of Sulaimaniyah where some of the 40 wounded had been taken.

The local police chief, Col. Ahmed Mahmoud Khalifa, said jobs in the police force are prized in Jalula, a mostly Sunni Arab town of 67,000 with a substantial Kurdish population, because unemployment runs high.

He said tribal sheiks had been asked to send recruits to the new police unit, and applicants came to the police center Tuesday to check whether they had been accepted.

"Today I was so happy to get a job at last to feed my wife and two kids," said Yasir Ramadan, 21, an applicant who was wounded by shrapnel and will need eye surgery. "I used to work as day laborer in construction. But there's no construction in the area, and it's hard to find work."

No group claimed responsibility for the bombing, although homicide attacks are the hallmark of Al Qaeda in Iraq and other Sunni Islamist extremists that operate in Diyala, among the most violent areas in the country.

The bombing occurred as U.S. and Iraqi forces are trying to rout Al Qaeda and other Sunni extremists from the Diyala River valley to the south of Jalula in the same province. U.S. and Iraqi officials describe Diyala province as the last major insurgent stronghold near Baghdad.

Two days ago, a homicide bomber blew himself up among well-wishers welcoming home an Iraqi detainee released from U.S. custody, killing at least 25 people on the western outskirts of the Iraqi capital.

The victims included members of a local U.S.-backed Sunni volunteer force raised to fight Al Qaeda.

Militants have often attacked police stations and recruiting drives to disrupt U.S.-led efforts to build up local security forces and undermine support for the insurgency.

Nevertheless, several wounded applicants, who were taken to a hospital in the Kurdish city of Sulaimaniyah, said they would not be deterred by the attack.

"We will beat terrorism and Al Qaeda," said Yasir al-Dulaimi, 18, who suffered injuries to his head and right arm. "We will not abandon our work. If we do so, we will abandon our honor as well because Al Qaeda would take full control over our area."

Elsewhere in Diyala, a roadside bomb killed five members of a Sunni family traveling Tuesday from Mandali on the Iranian border to visit a religious shrine. The dead included two women and two children, according to Col. Sarchal Abdul-Karim.

Also Tuesday, a bomb planted in a parked car blew up in the city of Tikrit, 80 miles north of Baghdad.

A police official initially said four people were killed. However, another police official later said he only received word of wounded, and security officials at a local hospital said they knew of 12 people injured in the blast.

Tikrit is Saddam Hussein's hometown and has been a hotbed of the Sunni insurgency since the 2003 ouster of the late Iraqi leader. But it has enjoyed relative quiet since violence levels significantly dropped over the past year in much of Iraq.