At least 16 people have been summarily executed in a retirement home in the Sheikh Osman district in Yemen in an assault allegedly perpetrated by the Islamic State.

According to a report by IBTimes, the victims included four Christian nuns, staff and elderly residents of the facility.

The assailants reportedly gained access to the facility after killing a security guard and proceeded to handcuff the employees and patients. They were later executed by the gunmen who were armed with automatic weapons.

Photographs of the scene of the crime showed the victims with their hands tied behind their backs lying lifeless in a pool of blood. They sustained gunshot wounds to the head, according to authorities.

The assailants were able to flee the scene of the crime before authorities arrived and those responsible for the attack have not yet been confirmed.

Both the Al Qaeda and the Islamic State (ISIS) have a strong presence in the area but the Daesh, a local branch of the ISIS have claimed responsibility for a series of deadly attacks in the Aden area, where the facility is situated, in the past couple of months.

A report by The Guardian indicated that there was one nun who survived the attack after hiding inside a fridge when she heard a guard's warning to run.

Sunita Kumar, a spokeswoman for Missionaries of Charity, an organisation established by Mother Teresa in Kolkata, the members of the charity were shocked by the incident.

"The sisters were to come back, but they opted to stay on to serve people," she said.

Two of the nuns that were killed were from Rwanda, while one was from India and another was from Kenya.

The violence in Yemen has so far caused the deaths of at least 6,200 civilians while 2.4 million people have been displaced by the conflict, UN figures indicate.