PIC: Swiss Guards parade before the Easter Sunday mass on Sunday at St Peter's square in Vatican. (AFP)

VATICAN CITY - Pope Francis began his traditional Easter mass in Rome on Sunday with thousands of the faithful being subjected to heightened security measures.

The Easter mass, the highlight of the Christian calendar, started at 0800 GMT (11am Ugandan time) under a cloudy sky where worshippers had gathered since the early hours to gain access. Heavy rain lashed down for several minutes around one hour later.

The mass followed Francis's Good Friday prayer in which he deplored the suffering of migrants, victims of racism and the persecution of Christians around the world.

Pope Francis leads the Easter Sunday mass at St Peter's square in Vatican

A nun stands on a terrace overlooking St Peter's square

A week of Easter events had a bloody beginning last Sunday when attacks claimed by the Islamic State group on two Coptic churches in Egypt left 45 people dead.

The entire area around St Peter's Basilica was blocked, with only several access points for those admitted after their bags had been inspected.

Access to St Peter's Square itself was only possible after security checks similar to those at airports. Hundreds of police and security forces stood guard.

Mass was to be followed by the traditional Urbi et Orbi blessing, to the city and the world, from the Argentine pope at around 1000 GMT (1pm Ugandan time).

ALSO RELATED TO THIS STORY

Pope blasts migrant suffering in Easter prayer