Rome: Pope Francis has expressed anguish over the killing of 16 people at a home for the elderly in Yemen.

The Vatican said on Saturday that the Pope was shocked and “profoundly saddened” to learn about the killing of four Missionaries of Charity and 12 others.

Four gunmen stormed a Missionaries of Charity home in Aden’s Sheikh Othman district on Friday, killing a guard before tying up and shooting employees. The dead included four Mother Teresa nuns – two from Rwanda and one each from India and Kenya. The superior of the convent Sister Sally managed to escape hiding in a refrigerator. An Indian Salesian priest, Fr Tom Uzhunnalil, who was staying in the convent premises, was missing since the attack. He was praying in the chapel when the attack took place.

Vatican’s Secretary of State Cardinal Pietro Parolin said in a statement that the Pope “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.”

Cardinal Parolin said the Pope prays that “this pointless slaughter will awaken consciences, lead to a change of heart, and inspire all parties to lay down their arms and take up the path of dialogue.”

The Pope also urged all parties to renounce violence, and renew their commitment to the people of Yemen, “particularly those most in need, whom the sisters and their helpers sought to serve.”

Although no group has claimed responsibility for the killing, officials in Yemen blamed ” the Islamic State group, which has been gaining ground in Aden in recent months.

It was established by Blessed Mother Teresa of Kolkata, founder of the Missionaries of Charity.

Al Jazeera reported that the gunmen forced the men and women outside with their hands tied. Screams of elderly residents echoed from the home during the shooting rampage. They later saw bodies of dead workers with their arms tied behind their backs scattered on the floor.

Aden was once a cosmopolitan city home to thriving Hindu and Christian communities, but its small Christian population left long ago.

Unknown assailants have previously vandalized a Christian cemetery, torched a church and last year blew up an abandoned Catholic church.

Yemen descended into a civil war in March when Houthi rebel fighters forced President Abd-Rabbu Mansour Hadi to flee to Saudi Arabia after they closed in on Aden, drawing in an Arab coalition assembled by the Saudis into the conflict.

The United Nations says nearly 6,000 people have been killed in the fighting, while hundreds of thousands have been displaced from their homes.