A general view is seen of Pope Francis leading the Easter mass in St. Peter's square at the Vatican March 27, 2016.

Pope Francis urged the world in his Easter message on Sunday to use the "weapons of love" to combat the evil of "blind and brutal violence", following the attacks in Brussels.

After a week of sombre religious events commemorating Jesus' death, Francis said an Easter Sunday Mass under tight security for tens of thousands of people in a sun-drenched St. Peter's Square.

Afterwards, in his traditional, twice-yearly "Urbi et Orbi" (to the city and the world) message, he spoke of violence, injustice and threats to peace in many parts of the world.

"May he (the risen Jesus) draw us closer on this Easter feast to the victims of terrorism, that blind and brutal form of violence which continues to shed blood in different parts of the world," he said, speaking from the central balcony of St. Peter's Basilica.

He mentioned recent attacks in Belgium, where at least 31 people were killed by Islamist militants, as well as those in Turkey, Nigeria, Chad, Cameroon, Ivory Coast, and Iraq.

"With the weapons of love, God has defeated selfishness and death," the leader of the world's 1.2 billion Roman Catholic said from the same balcony from where he first appeared to the world on the night of his election on March 13, 2013.

The 79-year-old Argentine pontiff urged people to channel the hope of Easter in order to defeat "the evil that seems to have the upper hand in the life of so many people".

The pope condemned the Brussels attacks several times during the past week, including at a Good Friday service where he said followers of religions who carried out acts of fundamentalism or terrorism were profaning God's name..

The former king and queen of Belgium, Albert II and Paola, who is Italian, attended the Mass and the pope greeted them afterwards.

In other parts of his address, Francis expressed the hope that recent talks could resolve the conflict in Syria in order to end the "sad wake of destruction, death, contempt for humanitarian law and the breakdown of civil concord".

He urged Europe "not to forget those men and women seeking a better future, an ever more numerous throng of migrants and refugees - including many children - fleeing from war, hunger, poverty and social injustice."

The European Union and Turkey have agreed to stop the flow of migrants to Europe in return for political and financial concessions for Ankara. Turkey and The Aegean islands have been the main route for migrants and refugees pouring into Europe in the past year.

Francis called for dialogue between Israelis and Palestinians, and resolutions to conflicts and political tensions in Yemen, Iraq, Libya, Burundi, Mozambique, the Democratic Republic of the Congo, South Sudan, and Ukraine.

Security was very tight around the square, which was bedecked with more than 35,000 flowers and plants donated by the Netherlands.

Police checked people several times at various points along the approach the square and subjected those with entry tickets to body and bag searches even before they passed through metal detectors. Security sources said police reinforcements had arrived in Rome from other Italian cities.

Islamic State militants have made threats against Catholic targets in Rome. Last year, a website used by militants ran a photo montage showing the movement's black flag flying from the obelisk at the centre of St Peter's Square.