A suspected Al-Qaeda gunman opened fire on a minibus carrying staff members from a military hospital in Yemen's main southern city of Aden on Sunday, killing eight people, an army official said.

The attacker used an assault rifle to rake the army minibus with gunfire, the official said. Two women were among the dead while 12 other staff members were wounded.

"The bus was carrying doctors and nurses working for the military hospital in Aden," the official said.

Among the wounded was "a mother who was with her two children on board" the bus.

The official accused Al-Qaeda of plotting and executing the attack, which comes as the army presses an all-out offensive it launched in late April against jihadist strongholds in Yemen's southern provinces of Shabwa and Abyan.

The army says 500 Al-Qaeda militants have been killed in the army's latest operation, while 40 soldiers died and 100 others were wounded.

It is not the first time Yemeni medical personnel have been hit by Al-Qaeda. In December, members of the jihadist group carried out a brazen attack on a defence complex in Sanaa that killed 56 people, among them a number of medics, including seven foreigners.

Taking advantage of a collapse of central authority during a 2011 uprising that forced veteran strongman Ali Abdullah Saleh from power, Al-Qaeda seized swathes of the south and east.

They remain deeply entrenched in Hadramawt province further east, where they have carried out a series of spectacular attacks in recent months.

In Hadramawt's provincial capital Mukalla, gunmen on a motorbike opened fire late Saturday on army Colonel Hassan Seif, who was seriously wounded and later died in hospital.

Seif headed a programme for demining towns in Yemen's east and southeast, a security official told AFP.

Al-Qaeda in the Arabian Peninsula (AQAP) has been blamed for previous motorbike attacks on security forces, despite never claiming them.

In December, Yemen enforced a temporary ban on motorcycles in the capital to prevent attacks as politicians held national dialogue talks.

On Friday, four Yemeni soldiers and five suspected Al-Qaeda militants were killed in two separate attacks in the south, military and local sources said.

Washington regards AQAP as the deadliest Al-Qaeda affiliate and has stepped up drone strikes against its leaders.