BAGHDAD — The latest in a wave of female suicide bombers killed 15 people and wounded more than 40 others on Sunday near a heavily fortified courthouse and government outpost in central Baqouba, Iraqi security officials said.

Seven of the dead and 10 of the wounded were Iraqi police officers.

The bombing was the most devastating of four attacks by guerrillas in Diyala province on Sunday that left at least 25 people dead and close to 60 wounded.

While Diyala is no longer under the almost complete control of Sunni insurgents and Shiite militias — as it was much of last year — a spate of attacks has prompted concerns about the endurance of recent security gains and the extent to which guerrillas in some areas still operate freely.

Hours after the explosion in Baqouba, a mortar volley struck north of Khalis, in the western end of Diyala, killing seven people and wounding 12, according to provincial police officials. The mortars were believed to have been fired from villages around Khalis, which one police official said "have seen a remarkable increase in the activities of the armed groups recently."

The bomber who struck in Baqouba, the provincial capital, wore a vest padded with powerful explosives and laced with small projectiles — apparently iron ball bearings, the officials said. The magnitude of the blast immediately raised questions about the sophistication of the bomb, which witnesses described as unusually strong.

"The explosion was huge, like it was a car bomb," said Adnan Majid, a 29-year-old library worker who was wounded in the arm. The bodies of at least three police officers were torn to pieces by the force of the detonation, security officials said.

Everyone near the government center, including women, must submit to searches, said Maj. Gen. Abdul Karim al-Rubaie, a senior security official in Diyala. But the bomber appeared to mill among a large number of pedestrians before quietly approaching the parked convoy.

Rubaie blamed the attack and other recent incidents involving female suicide bombers in Diyala on the insurgent group al-Qaida in Mesopotamia and on "takfiris," a catchall term used to describe Sunni extremists who attack Shiites because they believe Shiites practice a heretical form of Islam.

"They are recruiting these poor women and using them," he said, "and that reflects how bad and broken they are."

Despite the much touted decline in violence across Iraq, there have been a number of bloody strikes recently against Shiite and Sunni targets, demonstrating that anti-government guerrillas still have the wherewithal to carry out large attacks.