At least 16 people were killed on Friday when unknown militants targeted a home for the elderly in Yemen’s southern city of Aden.

The attack took place in the centre of Aden, which has seen an uptick in attacks and assassinations over recent weeks, Sky News Arabia reported.

Four of those killed were Indian nationals who were working as nurses in the centre, the agency’s correspondent reported.

Twelve of the centre’s residents were also killed when the militants burst in and began firing machine guns at random, a survivor told local news site Aden al-Ghad.

A source in the centre’s administration told Aden al-Ghad that four militants had gained access by telling the guard they were there to visit their mother.

One of the Indian nurses survived by hiding in the cold room used to store medication.

Unverified images purportedly from the scene showed bodies lying in a residential room in the centre, as well as the courtyard, having apparently been shot in the head.

The centre is run by a charitable organisation – it is not known why it was targeted.

People injured in the attack have been transferred to a local government-run hospital, as well as to a health centre run by Doctors Without Borders.

It was not immediately clear whether the gunmen escaped following the attack, and there has been no claim of responsibility.

Aden, once the capital of independent south Yemen, has been a key battleground in the bloody power struggle between Houthi rebels and supporters of exiled president Abd Rabbuh Mansour Hadi.

Hadi initially fled to Aden after being pushed out of the capital Sanaa in September 2014, but was later forced to flee to Saudi Arabia, which is leading a campaign of air strikes aimed at pushing back the Houthi rebels.

After nearly a year of chaotic fighting between supporters of the Houthis and of the exiled government, groups like Al-Qaeda in the Arabian Peninsula – and the Islamic State group – have taken advantage of a power vacuum and expanded their power base.

Aden’s governor survived a second assassination attempt earlier this month, after his convoy was targeted by three masked gunmen.