Pakistan's military was again targeted by militants when a suicide bomber on Monday rammed his motorcycle into a minibus carrying medical corps staff, killing at least 10 people and injuring 30 others, near the army headquarters in Rawalpindi.

The explosion occurred at 7.15 am outside the gate of the army's National Logistics Cell on a road connecting the Royal Artillery Bazaar to the General Headquarters in the nearby garrison city.

At least 10 people died in the attack, Geo News reported. A statement from the army confirmed the death of four security forces personnel but did not mention civilian casualties in the bombing, the first such attack since the December 27 killing of former premier Benazir Bhutto during an election rally in the city. Reports said a major was among the dead.

"It was a suicide attack. A man on a motorcycle rammed into the bus," a military official said.

The powerful blast completely destroyed the bus carrying trainee doctors from the Army Medical College to the Combined Military Hospital and some other vehicles, turning them into a mangled heap of metal.

Officials said the death toll could rise as several of the injured were in a serious condition.

This is the seventh suicide attack to rock Rawalpindi in the last six months.

A red alert was sounded across Punjab province following the blast, which came a day after security agencies directed the police in the twin cities of Islamabad and Rawalpindi to tighten security.