BAQOUBA, Iraq — Two suicide bombers blew themselves up in a crowd of army recruits Tuesday in an Iraqi province where devastating attacks persist despite security improvements elsewhere. At least 28 people died, the Iraqi police and military said.

The bombings came ahead of what Iraqi military officials have described as an imminent offensive in troubled Diyala province, northeast of Baghdad. The U.S. military says it will support that effort, which it called an enhancement of existing patrols and actions there.

Violence also flared in the northern city of Mosul, where a dozen people died in bombings on Tuesday, the U.S. military said.

The blasts at the Saad military camp in Baqouba, the capital of Diyala, recalled the scenes of mass terror and grief that were almost a daily routine in previous years. Violence in Iraq is at its lowest level in about four years.

AP Television News footage showed medical staff unloading white body bags from ambulances, soldiers on their knees weeping over slain comrades and the wounded moaning as they lay on gurneys and even on the bloodstained floor of a hospital room.

A man who suffered a leg injury said the first explosion drew a crowd that tried to evacuate victims. The second bomber then detonated his explosive vest among the rescuers, said the man, who did not want to be named because of safety concerns.

The explosions killed 28 people and wounded at least 57 recruits, a police official said. He spoke on condition of anonymity because he was not authorized to speak to the media.

A military officer in Baqouba, 35 miles from Baghdad, confirmed the death toll and said soldiers were among the casualties. He also spoke on condition of anonymity for the same reason.

The U.S. military said in a statement that the attack occurred around 8 a.m. It said 20 police recruits were killed and 55 were wounded. There was no immediate explanation for the discrepancy in the reports.

It was the bloodiest attack in Iraq since June 17, when a truck bombing killed 63 people in Hurriyah, a Baghdad neighborhood that saw some of the worst Shiite-Sunni slaughter in 2006.

Diyala is critical to Baghdad's security because of its strategic importance as an entrance to the capital and a threat to supply routes going north. The volatile, ethnically mixed area also borders Iran, which the United States has accused of helping militants to stage attacks on American troops.

Last year, U.S. troops largely subdued militancy in Baqouba, which had been held by al-Qaida in Iraq and other Sunni extremist groups. But many insurgents were believed to have melted away and now appear to be regrouping.

Loyalists of Saddam Hussein's regime had homes in Buhriz, a southern suburb of Baqouba, and the area served as a staging ground for Sunni attacks that drove Shiites out of the city.

Abu Musab al-Zarqawi, leader of al-Qaida in Iraq, was killed by a U.S. airstrike in Diyala province in June 2006.

On June 22, a female suicide bomber concealing explosives beneath her black robe struck outside a government complex in Baqouba. At least 15 people were killed and more than 40 were wounded. A car bomb across the street from the same compound killed at least 40 people in April.

The decline in violence in Iraq has been driven by a variety of factors, including the 2007 U.S. troop surge and a Sunni revolt against al-Qaida in Iraq. U.S.-backed Iraqi forces have scored successes in offensives against Shiite militants in Baghdad's Sadr City district and the southern cities of Basra and Amarah, and against Sunni extremists in Mosul in the north.

Iraq's Interior Ministry spokesman, Maj. Gen. Abdul-Karim Khalaf, said Sunday that the government's planned operation in Diyala would be "the last surge."

Al-Mada, an Iraqi newspaper, on Tuesday reported Khalaf as saying that the file on the Diyala operation had been handed to Prime Minister Nouri al-Maliki, who will decide when to launch it.

In western Mosul, a bomb near an Iraqi police station killed four Iraqi civilians, the U.S. military said. Half an hour later, one Iraqi police officer and seven civilians died in a suicide car bombing in the east of the city, the military said.

Three other bombs in Mosul wounded 15 people, including 11 police and soldiers, Iraqi authorities.

Also Tuesday, the U.S. military said it had captured the Iranian-trained leader of an explosives cell in the Adhamiyah district of Baghdad. It said the suspect has been linked to attacks against U.S. and Iraqi bases in the capital.