Egypt's Patriarch of Alexandria, a top leader of the Greek Orthodox church, was among 17 people feared killed when a helicopter crashed this morning off northern Greece, the Defence Ministry said.
Rescue crews searched for survivors some 30 km out to sea from the Mount Athos community of Orthodox monasteries where the military Chinook helicopter carrying Patriarch Petros was headed.
"All may be dead," a Greek Defence Ministry official said.
"We are shocked, this is tragic news," said a Church of Greece spokesman, Father Epifanios Economou.
The Patriarchate of Alexandria was established in 42 A.D. by Mark the Evangelist and was an early centre of Christianity and Orthodoxy.
"The Patriarchate of Alexandria and All Africa is one of the third oldest worldwide, along with that of Antioch (Syria) and Rome," said Father Costas Kyriakides, a theologian in Cyprus where Petros was born.
"It has always been extremely important. It carries a very heavy history and is very active in missionary field work in places like Kenya and Uganda," he said.
Fr Economu said the 55-year-old cleric was a respected church leader who had breathed new life into the patriarchate and to the entire Orthodox Church in Africa in his seven years in office.
He was elected as the 115th Patriarch of Alexandria and All Africa in 1997.
Patriarch Petros had been due to arrive on Mount Athos today around 11 a.m. and monks notified authorities as time passed that the helicopter was missing.
Fr Economou said the trip was to be the Patriarch's first official visit to the monastic region along with a group of clerics from his patriarchate and other dioceses in Africa.
Six clerics, six laymen and five crew were on board.