A huge explosion killed the governor of Yemen's southern Aden province and six of his bodyguards on Sunday, security officials said.

Gov. Gaafar Mohamed Saad was travelling to his office on Sunday morning when the explosion struck his convoy in the Rimbaud area of the southern port city. Authorities are investigating the exact cause of the explosion.

The officials spoke on condition of anonymity because they were not authorized to brief the media.

Pro-government forces backed by a Saudi-led coalition drove Shia Houthi rebels out of Aden earlier this year. A local al-Qaeda affiliate has exploited the chaos of Yemen's conflict to seize territory in the country's south and east, and has a growing presence in Aden.

On Saturday, masked gunmen on motorcycles carried out separate attacks on vehicles in Aden, killing Col. Aqeel al-Khodr, a military intelligence official, and Judge Mohsen Alwan, who was known for sentencing al-Qaeda militants. Three other people were killed in the attack on Alwan.

No one immediately claimed the attacks, which bore the hallmarks of al-Qaeda.

Al-Qaeda in the Arabian Peninsula, or AQAP, has long been seen as one of the most sophisticated branches of the global network and has been linked to several failed attacks on the U.S. homeland. The Yemeni affiliate claimed an attack on the Paris office of a French satirical magazine in January, which left 12 people dead.