A suicide bomb inside a car exploded outside the home of the security director for the southern Yemini city of Aden, killing four of his guards. Brigadier General Shalal Ali Shayyeh was also the target of a car bomb attack two weeks ago.

There's been an escalating wave of assassinations targeting security forces in the city. The government has been grappling with lawlessness since militants backed by a Saudi-led military alliance, drove out the Iran-allied Houthi group in July, but they haven't been able to impose control in Aden.

Ground fighting and air strikes have killed around 6,000 people, half of them civilians, during the nine-month war in Yemen.