The spiritual head of Orthodox Christians worldwide formally granted independence to the Ukrainian church on Saturday, marking a historic split from Russia which Ukrainian leaders see as vital to the country's security.
The decree, granting "autocephaly," was signed by Ecumenical Patriarch Bartholomew at a service with the head of the Ukrainian church Metropolitan Epifaniy and President Petro Petroshenko in St. George's Cathedral at the patriarchate in Istanbul.
The patriarchate, the seat of the spiritual leader of some 300 million Orthodox Christians worldwide, endorsed Ukraine's request for the new church in October.
Ukraine last month chose 39-year-old Metropolitan Epifaniy to head the new church, in a move which Poroshenko compared to Ukraine's referendum for independence from the Soviet Union in 1991.
The move incensed Moscow, and prompted President Vladimir Putin to warn of possible bloodshed in his annual news conference. Relations between Ukraine and Russia collapsed after Moscow's seizure of Crimea in 2014.
The Ukrainian Orthodox church has been beholden to Moscow for hundreds of years, and Ukraine's leaders see church independence as vital to tackling Russian meddling.