The Archbishop of Canterbury has renewed calls for the protection of civilians in Gaza after an explosion at an Anglican-run hospital left hundreds dead.

In addition to patients, the Al Ahli Hospital in Gaza City was sheltering civilians who had left their homes to avoid air strikes. 

"This is an appalling and devastating loss of innocent lives," said Archbishop Justin Welby.

"The Ahli hospital is run by the Anglican church. I mourn with our brothers and sisters - please pray for them. I renew my appeal for civilians to be protected in this devastating war. May the Lord God have mercy."

The Palestinian authorities have blamed the blast on an Israeli airstrike but Israel has claimed it was caused by a misfired rocket.

The tragedy happened just days after the Archbishop warned that the hospital's seriously ill and wounded patients could not be safely evacuated. 

At the weekend, the Archbishop had pleaded for the Israeli evacuation order in northern Gaza to be reversed and for the protection of hospitals and civilian lives. 

The hospital has existed in Gaza City since 1882. It is the oldest hospital in Gaza and the only Christian one. 

It is run by the Episcopal Diocese of Jerusalem, which has called for a day of mourning in churches. 

"Hospitals, by the tenets of international humanitarian law, are sanctuaries, yet this assault has transgressed those sacred boundaries," it said.

"We heed the call of Archbishop Justin Welby, who implored for the safeguarding of medical facilities and the rescission of evacuation orders. Regrettably, Gaza remains bereft of safe havens."