Yemeni security officials say a drive-by shooting killed a top pro-government militia leader and five of his companions in the southern city of Aden, just hours after he reluctantly handed over control of the city's strategic port to government troops.

The officials say gunmen opened fire from a speeding car early on Thursday, killing Ahmed al-Idrisi and five others as they were leaving a wedding party in the Mansoura neighborhood.

No one immediately claimed responsibility for the attack. The officials spoke on condition of anonymity in line with regulations.

Yemen's al-Qaida and Islamic State affiliates have exploited the country's civil war to run lucrative smuggling operations through the Aden port.

The officials claim that al-Idrisi publicly backed the internationally recognized government but maintained secret deals with extremists and anti-government forces.