GEOFF BENNETT: Russia first occupied the southern Ukrainian city of Melitopol in early March 2022.

And Russian Secret Services, after persecuting pro-Ukrainian activists, former government officials and human rights defenders, have since targeted the churches and their pastors and congregants.

With support from the Pulitzer Center, special correspondent Simon Ostrovsky and videographer Yegor Troyanovsky reports from Ukraine.

SIMON OSTROVSKY: All across Russian-occupied Ukraine, soldiers are shutting down places of worship that don't fit the world Vladimir Putin wants to build.

MIKHAYLO BRYTSYN, Pastor, Grace Evangelical Church: September 11, 2022.

It was Sunday.

It was worship service.

It's like 20 armed people with masks, military uniform, and they were very brutal.

MARK SERGEEV, Pastor, New Generation Church: They said: "You have to stop this.

You have to stop these meetings."

And he said: "I'm a pastor.

I cannot stop the will of the people."

And they said: "If you will not stop, you're going to see the blood."

SIMON OSTROVSKY: Mikhaylo Brytsyn and Mark Sergeev are ministers who once led their flocks in the Southern Ukrainian city of Melitopol, but no longer.

Since the occupation, evangelical congregations, Protestant churches, all the non-Russian Orthodox Christian faiths have been deemed undesirable and tens of thousands of believers have been forced to flee.

Those who remain gather in secret in private homes for fear of angering the new regime.

The head of that new regime makes himself out to be the defender of the faith, his faith.

With the client patriarch of the national church at his side, Vladimir Putin and his supporters make little secret of their plans to put Russian Orthodox Christianity above all other forms of Christianity.

This footage is from the Grace Evangelical Church.

The people gathered here don't know it's their last service in this building.

A Russian soldier stops the worship and tells the women and children to go downstairs to have their I.D.s checked.

No one knows what will happen next.

By this stage in the war, Russian forces had already killed five priests in the occupied parts of Ukraine.

MIKHAYLO BRYTSYN: They start to fingerprint everybody.

They copied their I.D., make pictures, addresses.

SIMON OSTROVSKY: To keep their spirits up, believers sing as they wait their turn to be questioned by Russian soldiers.

MIKHAYLO BRYTSYN: We were accused of being an extremist organization.

We were accused of being German spies and then American spies.

SIMON OSTROVSKY: Mikhaylo Brytsyn is pretty far from being a spy.

He's been a pastor at Grace Church since 1991, when the church building was given back to the evangelical community of Melitopol after being nationalized by the Soviet Union.

MIKHAYLO BRYTSYN: I was conveyed to their military vehicle, and they searched all church buildings.

They searched all my house.

And they told us to leave in two days.

SIMON OSTROVSKY: In two years of war, no denomination has been spared death and destruction.

This was an Orthodox church affiliated with Moscow, collateral damage in a Russian missile strike a year ago.

But two groups in particular have suffered the most in terms of sheer numbers.

And that's the Orthodox Church of Ukraine and Protestant churches that have come under extreme pressure in areas occupied by Russia.

MARK SERGEEV (through translator): A Baptist Protestant church.

It's still standing but everything is destroyed.

SIMON OSTROVSKY: At least 206 evangelical churches have been expropriated or destroyed, according to the Institute for Religious Freedom, a Ukrainian watchdog group.

Steven Moore is a former Republican congressional staffer and founder of the Ukraine Freedom Project, a nonprofit.

STEVEN MOORE, Founder, Ukraine Freedom Project: When the Russians come into a town in an occupied area, they see Protestant churches, they say, this is an American religion.

You must be an agent of the American government.

So they go to the churches.

They shut them down.

They frequently torture the pastor, and, sometimes, they murder believers for their faith.

And we know of 29 Christian leaders who have been murdered in Ukraine by the Russians.

MARK SERGEEV (through translator): Today, here in Melitopol, they blew up a Ukrainian tank.

The Russians came in the city maybe in 7:00 p.m. 24 of February.

I see like chaos in the whole city.

So many families, they're afraid to stay in the houses, in apartments.

Three weeks under the occupation of Melitopol, our church was the shelter for the people.

SIMON OSTROVSKY: New Generation Church was the largest in Melitopol and the first to draw the ire of the Russian occupation.

MARK SERGEEV: I think they are looking for us, because my father, like a senior pastor, when he preached, he always said that we have our own country, our own culture, and we have to pray for Ukraine.

SIMON OSTROVSKY: The Russian Security Services approached Mark's father several times, threatening violence to pressure him to publicly pledge loyalty to Russia.

MARK SERGEEV: And they said, if you will not stop, they're going to -- you're going to see the blood.

And they said, you have to record a video.

He has to record a video that Russia already here.

We have to just relax.

Putin is great president, and everything's OK.

But father said: "I will never do this."

SIMON OSTROVSKY: A day after this incident, Mark's father, Victor, was tipped off to leave the city as soon as possible because of the imminent threat to his life.

The whole family escaped to Ukraine-controlled territory.

A few days later, Russian soldiers stormed the church building and broke through the doors.

But they didn't stop there.

MARK SERGEEV: I remember this day.

I think I'm going to remember it for the whole of my life.

We are driving with my brother, and father called me and said: "Look, there's no cross anymore.

They just cut the cross."

SIMON OSTROVSKY: Russian forces searched Mark's home and broadcast the search on state-controlled television in a ham-fisted attempt to portray his family as an armed resistance cell.

MAN (through translator): We received information that there was a weapons cache in the building.

MARK SERGEEV: They showed like they found some bomb and the guns in the garage of my father and said, look, this is the pastor who works with the United States and with CIA.

SIMON OSTROVSKY: Meanwhile, the New Generation Church building was expropriated by Russia, the large cross that once stood out front replaced with a Russian flag.

Where people once prayed, officials hold secular events such as this citizenship ceremony.

MIKHAYLO BRYTSYN: There is no protest on churches in all occupied territory.

SIMON OSTROVSKY: So the only church still open in Melitopol is the Orthodox church affiliated with Moscow?

MIKHAYLO BRYTSYN: Yes.

This isn't the first time religion has faced persecution, priests have been killed, and churches are being shut down.

In the 1930s, when Stalin launched his infamous campaign of Red Terror, religious leaders of all denominations were targeted, including evangelists from Mikhaylo Brytsyn's church.

MIKHAYLO BRYTSYN: We get some documents from KGB archive, and we found the case when ministers of our church were accused during Stalin's terror, and these documents show that they were accused being extremists and German spies.

SIMON OSTROVSKY: Three pastors were put to death on the espionage charges, which were declared to be false after Stalin's death.

It's incredible how similar the language in the Soviet documents is compared to the modern Russian documents declaring your organization as an extremist organization.

And this was made in December of 2022.

The wave of religious persecution has forced most evangelists to flee Russian-occupied Ukraine.

Those who remain have to pray in secret.

MIKHAYLO BRYTSYN: I don't think that a lot of Americans know about Ukraine and all the more about Protestant in Ukraine.

It's part of my mission now is just to tell the truth, just to raise awareness of what happened in occupied territory.

SIMON OSTROVSKY: Mark, who was also forced to leave occupied Melitopol, is still a preacher.

His main job is now on the front lines with soldiers as a chaplain.

MARK SERGEEV: In the name of Jesus, let us defeat and destroy this enemy.

I wanted to say to the whole English-speaking world, we have so many Protestant churches in Ukraine, and they have to understand that so many pastors were killed.

We need weapons because Russia cannot stop.

Pray for Ukraine.

Still pray.

It's only us -- what I can ask you to do, really.

SIMON OSTROVSKY: For the "PBS NewsHour," I'm Simon Ostrovsky in Komyshuvakha, Ukraine.