The four suspected militants were killed when what was thought to be a US drone fired on a checkpoint at the entrance of the city of Azan.

At least four suspected al-Qaeda militants in southern Yemen were killed in what is believed to be a drone strike on Wednesday as unidentified warplanes bombed outposts held by the Islamist militant group further east, witnesses and local residents said.

The four suspected militants were killed when what was thought to be a US drone fired on a checkpoint at the entrance of the city of Azan in southern Yemen.

It was not immediately possible to confirm the accounts by the residents, who said the militants had seized the city two months ago. The United States has acknowledged using drones but declines to comment on specific attacks.

The stepped-up air strikes came as forces loyal to President Abdrabbu Mansour Hadi conducted a security operation against militants in al-Mansoura district of Aden, trying to end a state of chaos that had gripped the southern port city where the Yemeni government is temporarily based.

Al-Qaeda in the Arabian Peninsula and ISIS have exploited the year-old Yemen war between Hadi supporters, who are backed by a Saudi-led alliance, and Iran-allied Houthis militias to seize parts of the country, including the Hadramout provincial capital in southeastern Yemen.

Further violence

Residents said unidentified warplanes launched three strikes on a former Yemeni army camp east of Mukalla controlled by al-Qaeda late on Wednesday night.

They said the air strikes ignited a fire at the old al-Rayyan air base that could be seen from several miles away. Residents said they believed the attacks have caused casualties, but provided no figures.

The militants seized Mukalla in April last year, a month after a Saudi-led alliance began military operations trying to restore Hadi to power after he was forced to flee his temporary headquarters in Aden by the advancing Houthi forces.

Last week, US warplanes struck a training camp run by al-Qaeda, killing at least 50 people and wounding more than 30.

A local al-Qaeda commander said in an audio recording posted on the Internet on Wednesday that the camp was being used to train tribal volunteers to fight the Houthis.

The authenticity of the recording by the commander, identified as Saad bin Atef al-Awlaki, could not immediately be verified.

In Aden, a security official said Yemeni troops loyal to Hadi, backed by local fighters, deployed in the al-Mansoura district which resulted in the capture of at least 21 suspected militants.

Yemeni Prime Minister Khaled Bahah, who is also the vice president, is based in Aden.

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