SEOUL - Park Yu Chun, a member of K-pop boy band JYJ, has been accused of sexual assault by a woman in her 20s, according to a report.

Yonhap news agency said police are investigating after they received a complaint last Friday, alleging that Park raped her at a bar in Seoul early in the morning on June 4.

The woman is identified in reports as a Ms Lee who works in a nightspot.

In the police report filed by her boyfriend, she claimed that the assault happened in a bathroom of a room where she and Park had been drinking together, reported Yonhap.

She handed over her underwear as evidence.

She said she and Park did not know each other previously.

CCTV footage from the bar's hallway did not reveal anything significant, said police, adding that they will summon the two for questioning.

Park's agency C-Jes Entertainment denied the allegations. In a statement, it called the accusation "malicious threats" aimed at damaging a celebrity's reputation.

It said it would work with the police to uncover the truth.

Park, 30, started mandatory military service in Seoul last August .

He emigrated to the United States as a child but returned to South Korea after he was talent-scouted. He joined K-pop boy band TVXQ in 2003. Following a contract dispute, he and two other TVXQ members, Kim Jun Su and Kim Jae Joon, formed JYJ.

Park played the lead in the 2012 time-travel romance drama Rooftop Prince. At last year's Paeksang Arts Awards, he won Best New Actor for his role in the movie Haemoo (2014).