A man at an army recruitment center near the northern city of Mosul summoned volunteers trying to enlist to gather around him and then blew himself up, survivors said Friday. As many as 25 people were killed.

It was unclear whether the bomber was a recruitment official or someone posing as one.

Separately, two Marines were killed in western Iraq by insurgents firing small arms and rocket-propelled grenades, the U.S. military announced in a statement. The Marines belonged to Regimental Combat Team 2 of the 2nd Marine Division and were killed Thursday in a village west of Haditha, 125 miles northwest of Baghdad. Their names were not released.

Friday was the first day of army recruitment at the center in the village of Rabia, said Gen. Saeed Mohammed Jubouri, a police official. The village is near Mosul, a city frequently targeted by insurgents, and the Syrian border, which U.S. and Iraqi officials say foreign fighters cross to enter Iraq.

The attacker wore a belt of explosives hidden under his clothes, Jubouri said. He then detonated the explosives at the front gate to the army compound, Jubouri and other witnesses said.

"A man called us to register our names," said Arakn Mijbil, 25, who was being treated at a hospital for injuries. "It was very hot, and we wanted to give him our documents as fast as possible because of the heat. When we reached him, he blew himself up."

"I saw two of my friends die in front of me, and I couldn't go, because my leg had broken," he said. "I was screaming, but no one was listening to me. It was like doomsday."

Other survivors at the hospital gave the same account.

The U.S. military said in a statement that it had captured a cell leader of al Qaeda in Iraq, an insurgent group. Ammar Abu Bara, also known as Amar Hussein Hasan, was seized by U.S. soldiers Wednesday in Mosul, the statement said. Abu Bara became the leader for the Mosul area after a man who was allegedly the group's previous leader was captured last month, the military said.

Meanwhile, the chief investigative judge of Iraq's special tribunal told the Associated Press that former president Saddam Hussein was questioned during a 45-minute hearing Thursday about the brutal suppression of a Shiite uprising after the 1991 Persian Gulf War.

Judge Raeed Juhi told the AP that he soon expected to conclude the criminal investigation into events pertaining to the Shiite uprising and to Hussein's campaign in the 1980s to expel Iraqi Kurds from areas in the northern part of the country.

Hussein may be tried as soon as September for his alleged role in the 1982 massacre of more than 150 Shiites in Dujail, a village north of Baghdad -- the first in about a dozen trials that Hussein and his lieutenants are expected to face.

Knickmeyer reported from Baghdad.