The ex-wife of Orlando mass killer Omar Mateen claimed Monday that she believed he was homosexual — as it was revealed that he frequented the gay nightclub where he staged the nation’s worst massacre in modern times.

Sitora Yusufiy, who was married to Mateen in 2009 for three months, made the shocking claim on Brazilian television station SBT Brazil.

Her fiancé, Marco Dias, speaking in Portuguese on her behalf, said Yusufiy believed that Mateen had “gay tendencies” and that his father had called him gay in front of her. Dias also claimed “the FBI asked her not to tell this to the American media.”

The bombshell came as a male former classmate of Omar Mateen said he had been asked out romantically by the mass killer, who reportedly was a virtual regular at the Pulse nightclub, having visited it more than a dozen times over the years.

The former classmate said he would hang out with Mateen, hitting gay bars after attending class at Indian River Community College police academy in 2006 — and one time Mateen asked him out “romantically,” according to the Palm Beach Post.

“We went to a few gay bars with him, and I was not out at the time, so I declined his offer,” the former classmate told the paper.

The classmate told the paper he thought the killer, who pledged allegiance to ISIS before killing 49 at the gay nightclub Pulse, was gay and in the closet.

The classmate’s claims came after reports emerged that Mateen frequented the club for years before Sunday’s massacre.

“It’s the same guy,” Chris Callen, a drag queen who performs under the name Kristina McLaughlin, told the Canadian Press. “He’s been going to this bar for at least three years.”

Callen’s husband, Ty Smith, recalled seeing a drunk Mateen being escorted from the club.

“Sometimes he . . . would get so drunk he was loud and belligerent,” he told the Orlando Sentinel.

At least four Pulse clubgoers remembered seeing Mateen at least a dozen times in the past. But authorities said they had no further information when asked about the sightings on Monday. NBC reported that the FBI was looking into his alleged club visits.

“[He’d get] really, really drunk,” Smith told the Canadian Press. “He couldn’t drink when he was at home — around his wife, or family. His father was really strict . . . He used to bitch about it.”

Callen and Smith said they both stopped speaking to Mateen when he threatened them with a knife, after someone made a joke about religion.

“He ended up pulling a knife,” Callen explained. “He said if he ever messed with him again, you know how it’ll turn out.”

They also shot down claims that Mateen had snapped after seeing two men kissing each other in public.

“That’s bullcrap, right there. No offense. That’s straight-up crap. He’s been around us,” Smith said. “Some of those people did a little more than (kiss) outside the bar … He was partying with the people who supposedly drove him to do this?”

Kevin West, another regular at Pulse, told the Los Angeles Times that Mateen used gay dating apps on a regular basis and even messaged him on a gay dating app, Jack’d.

He even saw Mateen an hour before the shooting.

“He walked directly past me. I said, ‘Hey,’ and he turned and said, ‘Hey,’ ” and nodded his head, recalled West. “I could tell by the eyes [it was him].”

One Orlando man, who refused to be named, told MSNBC that he had seen photos of Mateen on several gay dating apps, including Grindr, Adam4Adam, and Jack’d. He claimed that at least two of the man’s friends had been contacted by Mateen on the apps in the past.

“He was very creepy in his messages, and I blocked him immediately,” the man said.

Here’s Mateen’s father saying that homosexuals should be punished by God: