Pope Francis has called for an end to the persecution of Christians in conflict, particularly in Africa and the Middle East, but also praised the recent nuclear agreement with Iran in his Easter message.

Speaking before a crowd braving rainy skies at St. Peter's Square after saying Easter mass, the Pontiff spoke on Christianity's most important liturgical feast day with memories of the April 2 massacre in Kenya still fresh.

"We ask Jesus, the victor over death, to lighten the sufferings of our many brothers and sisters who are persecuted for his name, and of all those who suffer injustice as a result of ongoing conflicts and violence - and there are many," said Francis.

The Pope also commented publicly for the first time on the basis for an agreement reached in Lausanne, Switzerland, on the same day as the massacre, aimed at a safeguard on Iran which has been accused of developing nuclear weapons.

"In hope we entrust to the merciful Lord the framework recently agreed to in Lausanne, that it may be a definitive step toward a more secure and fraternal world."

Armed guards were protecting Christian congregations at Kenyan churches from the al Shabaab extremist group claiming to represent Islam, as the Pope spoke during his customary Urbi et Orbi (to the city and the world address).

Al Shabaab terrorists massacred nearly 150 people, executing Christians who were singled out the day before Christianity commemorates the crucifixion of Jesus on Good Friday.

"May constant prayer rise up from all people of goodwill for those who lost their lives," said Francis.

"I think in particular of the young people who were killed last Thursday at Garissa University College in Kenya - for all who have been kidnapped, and for those forced to abandon their homes and their dear ones."

SYRIA AND IRAQ

He asked for peace in Syria and Iraq, "that the roar of arms may cease and that peaceful relations may be restored among the various groups which make up those beloved countries.

"May the international community not stand by before the immense humanitarian tragedy unfolding in these countries and the drama of the numerous refugees."

Pope Francis denounced the general prevalence of weapons in the world noting, "And we ask for peace for this world subjected to arms dealers, who earn their living with the blood of men and women."

The Archbishop of Canterbury, Justin Welby, the most senior bishop in the 88-million strong Anglican Communion said in his Easter message that the message of the Church at Easter remains constant over the centuries.

It proclaims "in the midst of hopelessness the hope of Christ, triumphant beyond death and the powers of evil; living and life giving amongst us."

He also noted this is a, "a world in which our brother and sister Christians are still a beleaguered and even persecuted community in many places, as they have been at different times and places in history. We continue to remember the suffering Christians in the Middle East.

"This year our remembrance is also focussed particularly on the Armenian people who a century ago were driven to their death and into exile because they were Christians."

At the same time, the Religious Liberty Commission of the World Evangelical Alliance on April 4 called for an international coalition to fight against terror that is impacting Christians.

"It's an unfortunate race among terror groups to cause destruction of human lives to maintain their relevance at a time when ISIS (Islamic State) is causing unprecedented bloodshed.

"This trend demands that the international coalition fighting ISIS in Iraq and Syria should expand their mission to include other terror groups as their targets - of course, not with airstrikes or troops on the ground," said Godfrey Yogarajah of the WEA commission.

"World leaders should join hands to defeat terrorism by cooperating with each other and treating the end of terrorism in every country as a common objective."