Pope Francis has called for the release of hostages in conflict zones in prayers conducted yesterday at the Vatican.

Crowds gathered in St Peter's Square for the Pope's Regina Caeli prayer, a liturgy for the Easter period in Catholic tradition.

Francis spoke from the window of the papal apartments. He said: "Dear brothers and sisters, in the hope given to us by the risen Christ, I renew my appeal for the release of all hostages in zones of armed conflict."

He made a special mention of the priest abducted during a raid by Islamic State forces on an old people's home in Yemen last month.

"In particular I would like to recall the Salesian priest Tom Uzhunnalil, kidnapped in Aden in Yemen on March 4," he said.

Uzhunnalil, from Bangalore in India, was kidnapped by the gunmen who murdered four Indian nuns, two Yemeni female staff members, eight elderly residents and a guard. Internet rumours said his captors would crucify him on Good Friday, but no evidence for the claim was ever produced and both his superiors and the Indian government consistently denied it.

Aden has been racked by lawlessness since supporters of Yemeni President Abd-Rabbu Mansour Hadi, backed by Gulf Arab military forces, drove fighters of the Iran-allied Houthi group from the city in July last year. International aid groups have pulled most of their foreign staff from Yemen due to security concerns.

A shaky truce took hold in the country today under a UN-backed effort to end a war that has made the country a front in Saudi Arabia's region wide rivalry with Iran and caused one of the world's worst humanitarian crises.

The war-damaged capital Sanaa spent a quiet night, witnesses said, but residents said fighting flared in the southwestern city of Taiz soon after the planned start of the cessation of hostilities at 9pm GMT on Sunday.

Additional reporting by Reuters.