Pope Francis has urged world leaders to try again to bring peace to Libya and in Syria, where millions of refugees and people displaced by conflict should be helped to return home.

In his traditional Easter Sunday address to the faithful at the Vatican, where some 70,000 were gathered in Saint Peter's square, the pope also expressed his "sadness" at news of the deadly bomb attacks on churches and hotels in Sri Lanka.

Pope Francis noted how in Libya violence has flared up again as strongman Khalifa Haftar's Libyan National Army attacked Tripoli, seat of the UN-backed government.

"May conflict and bloodshed cease in Libya, where defenceless people are once more dying in recent weeks," Pope Francis said.

"I urge the parties involved to choose dialogue over force and to avoid reopening wounds left by a decade of conflicts and political instability."

In Syria, where President Bashar Al-Assad has steadily recovered territory lost to rebel groups, the pope lamented the fate of "the beloved Syrian people, victims of an ongoing conflict to which we risk becoming ever more resigned and even indifferent."

"Now is instead the time for a renewed commitment for a political solution able to respond to people's legitimate hopes for freedom, peace and justice, confront the humanitarian crisis and favour the secure re-entry of the homeless, along with all those who have taken refuge in neighbouring countries, especially Lebanon and Jordan."

The pope noted how Easter, the holiest Christian festival, "makes us keep our eyes fixed on the Middle East, torn by continuing divisions and tensions."

Turning to South Sudan, Pope Francis urged rival leaders President Salva Kiir and rebel chief Riek Machar - who met recently at the Vatican - to sink their differences to pursure national reconciliation.

Yesterday, Mr Kiir called on Mr Machar to return home "urgently" to help form a government of national unity.