Aden descended into lawlessness after a Saudi-led coalition recaptured the city from Shiite Houthi rebels last summer.
Four Indian nuns are among 16 people killed in a terror attack on a retirement home in Yemen on Friday.
Yemeni security officials said gunmen entered the retirement home in the southern city of Aden around 12.30 in the afternoon.
According to the foreign ministry, two to four terrorists asked the guards to open the gates saying they wanted to visit their mothers.
On entering, they shot the gatekeeper dead instantly and opened fire.
Reports from Yemen said the terrorists separated the nuns from the others and shot them. The reports also said they later handcuffed the elderly people and opened fire.
The home is located in the Sheikh Osman district in Aden.
The nuns were from the Missionaries of Charity founded by Mother Teresa.
"We are trying to ascertain the details of the Indian victims," a foreign ministry official said.
Aden descended into lawlessness after a Saudi-led coalition recaptured the city from Shiite Houthi rebels last summer.
The terror group ISIS has claimed responsibility for a wave of deadly attacks in Aden, including a suicide bombing that killed the governor and several assassination attempts on top officials.