Fighters loyal to Yemen's President Abedrabbo Mansour Hadi sit in a pick-up truck in Ataq, the capital of the Shabwa province, east of Aden.

Reuters/Doha

Unidentified gunmen shot dead a Yemeni army colonel and a southern resistance leader in Aden on Tuesday night, a local official said, the latest in a string of assassinations in the city often carried out by Islamist militants.

The gunmen opened fire on a car containing resistance leader Jalal al-Awbali and the unidentified colonel in the Dar Saad district of northern Aden, killing them both immediately, the official said.

Islamist militants from both al Qaeda in the Arabian Peninsula (AQAP) and the Yemeni wing of the Islamic State group have staged attacks throughout southern parts of Yemen, including in Aden, for years.

The rate of attacks in Aden has accelerated since July, when local forces backed by the government of President Abedrabbo Mansour Hadi and a Saudi-led military alliance recaptured the city from the Houthi militia after months of street fighting.

Insecurity in Aden, the biggest prize yet won by Hadi in Yemen's nine-month civil war, threatens to undermine the campaign waged on his behalf against the Houthis and army units loyal to former president Ali Abdullah Saleh.

In a sign of growing international concern over Yemen's security problems, a US drone strike killed four suspected AQAP militants in central Yemen on Tuesday, the first such attack since September.

Western nations have been quietly increasing pressure on Saudi Arabia to seek a political deal to end the conflict, UN diplomats have said. The country's warring parties have accused each other of violations of a ceasefire that began on December 15.

Drone strike kills four Qaeda suspects

A presumed US drone strike has killed four suspected members of al Qaeda in central Yemen, a security official said on Wednesday.

The raid targeted their vehicle on Tuesday evening near the border of Baida and Shabwa provinces, the official said.

The US is the only country known to operate armed drones over Yemen.

It has kept up strikes on militants during months of fighting between pro-government forces and Houthi rebels who control the capital.