Suspected Al-Qaeda members killed five police officers on Friday in an attack in Yemen's second city of Aden, a security source said.

The masked assailants attacked a police outpost in the Basateen area of northern Aden before fleeing, the source said.

The incident came a day after three pro-government soldiers were killed by suspected jihadists in the southern port city.

Al-Qaeda controls parts of Aden, where the government of President Abd Rabou Mansour Hadi has set up base in its battle against Shia Houthi rebels who control the capital Sanaa.

With support from a Saudi-led coalition, Hadi's forces have driven the rebels out of Aden and four other southern provinces since last July but the Shia rebels control much of the north.

Al-Qaeda and the rival Islamic State militants group (ISIS) have taken advantage of the conflict to gain ground in southern cities such as Aden.

They have claimed a string of attacks and assassinations in recent months.

The UN says that the war in Yemen has killed more than 6,100 people since March, more than half civilians, and wounded more than 29,000.