Uber boss Travis Kalanick and five of his employees visited a sleazy “escort-karaoke” bar in South Korea — a fact that one top Uber exec has scrambled to keep quiet in recent weeks, according to a report.

Kalanick’s ex-girlfriend Gabi Holzwarth says she was with Kalanick and the higher-ups at Uber in mid-2014 when they went to the seedy Seoul saloon, where miniskirt-clad women “sat in a circle, identified by numbered tags,” according to The Information (paywall), a tech news site.

“Four male Uber managers picked women out of the group, calling out their numbers, and sat with them,” according to Holzwarth, the site reported over the weekend.

Holzwarth, a 27-year-old concert violinist who split up with Kalanick last summer, says she and Uber’s CEO left the bar about an hour later.

But that was after other men in the group picked out women to go downstairs and “sit with” in private rooms, Holzwarth said, adding that she didn’t know what happened afterward.

“After picking women, visitors typically headed downstairs to get acquainted with the women and sing karaoke before going home with them,” according to the report.

One of the execs in the circle, however, was a female marketing manager who later told Uber’s HR chief that the incident made her uncomfortable.

“[I]t made me feel horrible as a girl (seeing those girls with number tags and being called out is really degrading),” the female manager later told Holzwarth in a messaging exchange.

The name of the female manager wasn’t disclosed.

About three weeks ago, after Uber engineer Susan Fowler went public with sex harassment allegations, the report said Uber’s senior VP of business Emil Michael called Holzwarth, worried that details of the Seoul incident might get leaked.

“I just want to make sure that if this story comes out,” Holzwarth would stick to a phony script, saying she and Uber brass “went to karaoke and ‘had a good time,’” Michael said, according to Holzwarth.

In a written statement, Michael said, “Given the intense news cycle I thought it was the right thing to do to reach out and let her know that reporters may try to contact her directly.”

Michael — who caused a fracas in 2014 when he suggested that Uber dig up dirt on reporters who wrote negative stories about the company — added that “her recollection of this conversation was different from mine and I am very sorry if the purpose of my call was misunderstood.”

After the Seoul incident, Holzwarth said she later overheard Kalanick talking to the distressed marketing manager on the phone, asking her, “Are you OK, girl?” and telling her he wished she had come forward sooner.

Kalanick then hung up and said the woman “must have a lawyer and wants something,” according to Holzwarth.

It’s not clear how the HR complaint was resolved, but the woman appears to be still employed at the company, according to the report.

A few weeks ago, Holzwarth said she got text messages from Michael saying, “Remember that night in Korea? … We just went to a karaoke bar and that’s all that happened, right?”

Holzwarth notified Uber’s head of public policy and PR, Rachel Whetstone, who in turn notified former US Attorney General Eric Holder, who is now conducting an internal investigation over sex harassment complaints at Uber.

In a text-message exchange shortly thereafter, Kalanick denied any knowledge of Michael’s approach to Holzwarth. A day later, Kalanick sent another message to Holzwarth, asking how she was doing.

After Holzwarth said, “I can’t speak to you anymore,” Kalanick said he didn’t understand why, according to the report, and that he was “going through a tough time and it’s really nice to talk to someone.”