Christians in occupied regions of Ukraine are being driven underground by the hostility of pro-Russian forces who have been closing churches and arresting pastors, says Release International.
In the Russian-controlled city of Melitopol, occupying forces have shut the three largest evangelical Protestant churches.
At Grace Baptist Church, the congregation was in the middle of a worship service when it was raided on 11 September and forcibly closed by Russian troops.
According to Hyun Sook Foley, of Release partner organisation Voice of the Martyrs Korea, the pastor of the church was given 48 hours to leave the city.
"They entered the sanctuary while the congregation was singing a hymn, halted the worship service, registered the names of all present and detained several ministers," she said.
A month earlier, Melitopol Christian Church, whose auditorium can hold 1,000 people, was shut down by occupying forces.
It is reported that the cross was torn down and that the building has been turned into a 'cultural sports entertainment complex'.
In Chkalovo, a village close to Melitopol, Russian forces closed down a church on 21 September while an evening service was underway.
A soldier is reported to have told the congregation, "Your feet will not be here after the referendum. We have only one faith: Orthodoxy."
In Mariupol, a port city also under Russian control, armed soldiers wearing masks detained the pastor of Kurchatov Church, Leonid Ponomaryov and his wife Tatyana, raided their home and sealed off the church.
Mariupol lies within the Donetsk region, which was illegally annexed by Russia on 5 October. Release partner Forum 18 says that churches in this region have been searched and closed down, and religious leaders have been arrested and told to sever their ties with Ukrainian religious bodies.
In the city of Lysychansk, in the Luhansk region, occupying forces reportedly seized the Lysychansk Christian Centre and threw all the books from its library, including Bibles, into a neighbouring yard. These have been gathered up and hidden by local Christians.
Release International CEO Paul Robinson said it came as "no surprise" that Russian occupying forces are closing Protestant churches and detaining pastors.
"They've been doing the same since they seized and illegally annexed Crimea in 2014. This has set the pattern for what has followed," he said.
He warned that the persecution is driving Christians in these regions underground.
"In Crimea and other occupied territories, they have raided places of worship, closed churches, banned missionary activity, fined people for leading worship meetings, seized religious literature and forced religious communities to re-register with the state, refusing re-registration to the vast majority," he said.
"And now we are seeing churches raided, sealed and shut down, and the disappearance and detention of pastors in the occupied areas.
"Ukrainian Christians have been here before. They are begin driven back to the underground churches of the Soviet era. Yet the message of history should be clear to Russia: the Christian faith has survived 70 years of Soviet totalitarian rule, and it thrives today in China under similar conditions. Persecution can only strengthen the church."