A colonel in the Yemeni air force and a police officer were killed in separate attacks in south Yemen on Tuesday, military and police officials said.

Colonel Amin al-Shami, a pilot instructor, was killed when a bomb hidden in his car exploded as he was leaving a military base in the southern Yemeni province of Lahij, a military official told AFP.

Two others, both air force technicians, were wounded in the explosion.

A witness who spoke to AFP on condition of anonymity said "the bomb immediately killed the colonel, and the two others travelling with him were taken to the hospital."

Attacks on military officers have increased in recent months as embattled President Ali Abdullah Saleh loses his grip on power amid widespread protests demanding that he step down.

In the southern provinces, government troops have lost control of several towns to Al-Qaeda-linked militants and remain embroiled in near-daily battles to take them back.

In the southern port of Aden, meanwhile, a suicide bomber killed one policeman and wounded two more, police told AFP.

"A suicide bomber on foot detonated his explosives near a parked police vehicle outside the local office of the tourism ministry, killing one officer and wounding two others," the source said on condition of anonymity.

A resident of the Al-Tawahi district where the attack took place said the bomber was blown to pieces in the blast, which was followed by intense gunfire.