BAGHDAD: A suicide car bomb devastated a Shiite mosque in northern Iraq, one of a series of attacks today that killed at least 37 Shiite pilgrims and worshippers, police and medical officials said.

The incidents are the latest in a series that have targeted Shiites, raising concerns that insurgents are stepping up attacks, hoping to re-ignite sectarian violence that nearly tore the country apart in 2006 and 2007.

Though violence has dramatically declined in Iraq in the past two years, US officials have repeatedly called the security gains fragile and cautioned that a waning insurgency still has the ability to pull off sporadic, high profile attacks.

The deadliest blast occurred in Rasheediyah, north of Mosul, when a suicide car bomb struck a mosque, killing at least 30 people and trapping dozens more underneath the rubble, said a police official in Ninevah operations command.

The official said at least 88 were injured in the blast. Bodies were still being pulled from the rubble, the official said.

The attack occurred shortly after 1 p.m. as worshippers were leaving Friday prayers. The blast also severely damaged a dozen other buildings near the mosque, the official said.

In Baghdad, roadside bombs targetted Shiite pilgrims returning from the southern holy city of Karbala.

The first of three bombs exploded at about 9:10 a.m., targetting a minibus with pilgrims as it entered the Shiite slum of Sadr City, a police official said. The blast killed four pilgrims and wounded eight others, the official said. The casualities were confirmed by a medical official. A short time later, two near simultaneous explosions near the Shaab football stadium in eastern Baghdad killed three pilgrims as they were walking home to Sadr City, said another police official.

Thirteen pilgrims also were wounded in the two blasts, which occurred less than half a mile apart, the official said.