At least 16 people, including four Indian nurses, were killed when gunmen opened fire Friday at an elderly care home in Yemen’s main southern city of Aden, security officials said.

At least 16 people, including four Indian nurses, were killed when gunmen opened fire Friday at an elderly care home in Yemen's main southern city of Aden, security officials said.

Four gunmen stormed the facility housing dozens in Aden's Sheikh Othman district, killing a guard before tying up and shooting employees, the officials told AFP.

Screams of elderly residents echoed from the home during the shooting rampage, witnesses said.

They told AFP that they saw bodies of slain workers with their arms tied behind their backs scattered on the floor as the aged residents cried out in fear.

The dead nurses were Indian nuns, the officials said, adding that the rest of those killed were Yemenis working at the home.

Commenting on the attack, Pope Francis slammed it as “diabolical", the Vatican's Secretary of State Pietro Parolin said, adding that the Pope was shocked.

"His Holiness Pope Francis was shocked and profoundly saddened to learn of the killing of four Missionaries of Charity and 12 others at a home for the elderly in Aden," Cardinal Parolin said statement.

"He sends the assurance of his prayers for the dead and his spiritual closeness to their families and to all affected from this act of senseless and diabolical violence," he added.