A bomber has killed at least 42 people and injured 55 in an attack at a college in eastern Baghdad, police say.

Witnesses said a man detonated his jacket after being challenged by guards at the main entrance.

Earlier, at least four people were injured in a car bombing in the city's Karrada district, and one was killed in an explosion near the Iranian embassy.

A mortar was also fired into a Shia area in the south of Baghdad, injuring two people.

The attacks came a day after more than 40 people died in a truck bomb attack near a Sunni mosque in the town of Habbaniya, to the west of Baghdad.

At least 60 people were injured in the blast, which came only hours after Iraqi Prime Minister Nouri Maliki said sectarian killings had fallen as a result of the recent security surge.

'Mehdi Army's college'

Most of the victims of Sunday's blast at the College of Administration and Economics were students, police and witnesses said.

"There was an explosion. I did not feel anything for 15 minutes and when I returned to consciousness, I found myself in the hospital," Muhanad Nasir, a 22-year-old student, was quoted as saying by the Associated Press news agency.

Higher Education Minister Abed Dhiab al-Uljaili said most of the victims were students who had gone to sit exams and that five guards were among the dead, AFP news agency reported.

The agency said terrified parents converged on the scene, some collapsing in horror at the sight of blood and flesh at the entrance to the building.

The college is part of al-Mustansiriyah university, Baghdad's second largest.

It is controlled by the powerful Shia militia, the Mehdi Army, and had received threats warning it to close.

It is not the first time the university has been targeted.

Last month, more than 100 students were killed in a co-ordinated attack involving two car bombs and a suicide bomber at the university's main building.

Photo caption

The scene of a car bomb blast in central Baghdad