ISTANBUL (Reuters) - Ecumenical Patriarch Bartholomew, the spiritual head of Eastern Orthodox Christians worldwide, called overnight for the opening of humanitarian corridors in Ukraine where he said "an indescribable human tragedy is unfolding".

       Bartholomew, who has previously called for an end to war in Ukraine, said that he hoped this year's Easter would be "the impetus to open humanitarian corridors, safe passages to truly safe areas for the thousands of people surrounded in Mariupol."

       "The same applies to all other regions of Ukraine, where an indescribable human tragedy is unfolding... We call once again for an immediate end to the fratricidal war, which, like any war, undermines human dignity," Bartholomew said after an Easter service in Istanbul, where he is based.

       The leader of the Russian Orthodox Church, whose backing for Moscow's "special military operation" in Ukraine has dismayed many fellow Christians, said on Saturday he hoped it would end quickly but again did not condemn it.

       In 2019, Bartholomew, the spiritual head of some 300 million Eastern Orthodox Christians worldwide, granted autocephaly to the Orthodox Church of Ukraine, making it independent, in a historic split strongly opposed by Russia.

       (Reporting by Murad Sezer; Writing by Daren Butler; Editing by Raissa Kasolowsky)