Parishioners watched in horror as a massive four-alarm fire engulfed a Serbian Orthodox church in Manhattan on Sunday — hours after hundreds celebrated Easter services, authorities said.

“For this to happen on such a holy day, I don’t know what to say,” said Alex Velic, a 31-year-old churchgoer, as enormous fireballs erupted from the shattered windows of the Serbian Orthodox Cathedral of St. Sava on West 25th Street.

“To see it burning like that is such a shock. It’s just so sad,” he said. “I can’t think of the words to express how I’m feeling.”

A force of 170 firefighters responded to the fire, which started shortly before 7 p.m., FDNY officials said. Church officials and the FDNY both said there were no reports of major injuries, though three firefighters and a church caretaker had minor smoke inhalation.

“Nobody is hurt, everyone is safe,” explained Father Djokan Majstorovic, dean of the cathedral.

Fire Commissioner Daniel Nigro said there had been 700 people inside the church earlier in the day for the Orthodox Easter service. He added that the cause of the fire at the historic house of worship is still under investigation.

“It’s a very sad day today,” Nigro said. “They had their Mass at 10 a.m. and then a luncheon. The good news is that there was no one inside when the fire started and there are no injuries. One man is being checked out for smoke inhalation.”

Photos on Twitter showed flames shooting out the windows of the church as clouds of smoke billowed out the side.

Velic said his stepfather, Slobodan Ljubenko, 69, was the man who had to be checked for smoke inhalation after he ran inside the church to assess the scene.

“We looked outside and we could see the flames coming out from the windows,” he said. “My stepfather went inside the church to check out what was going on. He’s okay. He (was) treated for some smoke inhalation.”

Lubys Santos, 23, was on her way to work at The 40/40 club across the street from the church when the drama unfolded.

“I could feel the heat on my face,” she said. “I was across the street and I just started sweating. That’s how strong the flames were. People were outside and yelling in different languages. I saw a man who was just standing and crying. He might have been a member of the church.”

The FDNY could not yet identify a cause for the fire, but Velic noted that the Easter ceremony involved many candles.

“I can only imagine there were thousands of people coming to this church lighting candles,” he said. “The candles may have caused it.”

The Serbian Orthodox Cathedral of St. Sava was consecrated in 1855 as an Episcopal church called Trinity Chapel. It has been Serbian Orthodox since the 1940s, according to the church’s website.