The Vatican says Pope Francis was "shocked and profoundly saddened" by a murderous attack at a home for the elderly in southern Yemen that killed 16 people, including four nuns.

The Vatican secretary of state said in a condolence message on Saturday that the pontiff "prays that this pointless slaughter will awaken consciences, lead to a change of heart, and inspire all parties to lay down their arms."

Officials and witnesses in Yemen said gunmen on Friday stormed a retirement home run by a charity established by Mother Teresa, moving room to room handcuffing the victims before shooting them in the head.

The pope sent prayers for the dead and expressed his spiritual closeness to those affected by this "this act of senseless and diabolical violence."