April 5, 2015: Pakistani Christians chant prayers during Easter service in Karachi, Pakistan. (AP)

Christians in the Holy Land and across the world are celebrating Easter, commemorating the day followers believe Jesus was resurrected in Jerusalem 2,000 years ago.

The cavernous Holy Sepulcher church in Jerusalem was packed with worshippers on Sunday. The site is where Christians believe Jesus was crucified, buried and resurrected.

A Mass is expected later in Bethlehem’s Nativity Church, built atop the site where Christians believe Jesus was born.

Catholics and others are celebrating Easter whereas Orthodox Christians, who follow a different calendar, were marking Palm Sunday with processions.

At the Vatican, Pope Francis presided over a solemn vigil service Saturday night. In his homily, Francis said the Easter mystery requires the faithful to seek an answer “to the questions which challenge our faith, our fidelity, and our very existence.”