Another female carried out a suicide bomb attack killing 15 people and wounded at least 40 other on Sunday in central Baquba, local authorities said. The woman detonated her explosive laden vest near a fortified courthouse and government outpost. The lists of casualties included several policemen - seven dead and 10 wounded.

The female suicide attack was the deadliest of four similar attacks carried out by guerrillas on Sunday in Diyala, one of Iraq's most dangerous regions, where U.S. and Iraqi forces battle insurgents. At least 25 people died and 60 were wounded on that day in Iraq.

Just a few hours after the Baquba blast, a mortar volley struck north of Khalis, in the western end of Diyala. The explosion killed seven people and wounded 12, provincial police officials said. Local police said they believe the mortar shells had been fired from villages around Khalis.

The Baquba blast’s magnitude made investigators suspect that terrorists now have more sophisticated bombs. Eyewitnesses said that the suicide woman wore a vest padded with powerful explosives and laced with small projectiles, which appeared to be iron ball bearings.

“The explosion was huge, like it was a car bomb,” said Adnan Majid, a 29-year-old library worker who was wounded in the blast, The New York Times reported.

This was the 21st suicide mission carried out by a woman in Iraq this year according to the U.S. military. The al-Qaida and other Sunni militant groups are struggling to regroup after suffering great losses in the latest clashes with the U.S. and Iraqi forces in the area.