Orthodox Christians are gathering around the world to celebrate Easter.

Followers mark their faith's most important festival day on 28 April, one week after fellow Christians.

The different dates arise from use of the Julian calendar instead of the Gregorian calendar.

Image copyright AFP/Getty Image caption Believers marked the occasion in the same way they have for centuries in the Church of the Holy Sepulchre in Jerusalem

Image copyright AFP/Getty Image caption The ceremony involves "sacred fire" appearing from two cavities on either side of the Holy Sepulchre

Image copyright AFP/Getty Image caption Some pilgrims wore a "crown of thorns" in Jerusalem's Old City

Image copyright EPA Image caption In Greece on Friday, Orthodox Christians performed a procession in the sea

Image copyright AFP/Getty Image caption People throughout Greece celebrated Good Friday with religious icons and services

Image copyright Reuters Image caption A member of the Greek Orthodox clergy at the Church of the Holy Sepulchre in Jerusalem's Old City

Image copyright EPA Image caption The head of the Bosnian Serb Orthodox Church in Bosnia and Herzegovina conducts an Easter service

Image copyright EPA Image caption A priest blesses Orthodox believers during an Easter ceremony at St George Church in Istanbul

Image copyright Getty Images Image caption Christians attend an Orthodox Easter service in the Kurdish-controlled city of Qamishli in north-eastern Syria

Image copyright AFP Image caption A North Macedonian Orthodox priest leads a midnight Easter service in the village of Kalishta

Image copyright EPA Image caption Ukrainians light candles with the Holy Fire during an Orthodox Easter Mass at St Volodymir Cathedral in Kiev

Image copyright EPA Image caption A Ukrainian priest (R) blesses believers waiting for the start of an Orthodox Easter Mass with baskets of painted eggs and kulichi, a traditional Easter cake, in Kiev

Image copyright AFP Image caption Greek Orthodox Patriarch of Jerusalem Theophilos III (C) leads the Easter Sunday traditional procession toward the Church of the Holy Sepulchre in Jerusalem's Old City

Image copyright AFP Image caption A young girl closes her eyes as she and other Serbian Orthodox Christians hold candles during a midnight Easter service at a monastery in the village of Sukovo

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