PHOTOS: Chinese model Luo Zilin fired over frolic with Naomi Campbell's ex Boyfriend

Luo Zilin represents China at the 2011 Miss Universe pageant in Sao Paulo, Brazil. (Photo/Xinhua)

Former Miss Universe China Luo Zilin has been sacked by her agency for "unprofessional conduct" after she was spotted cozying up to Russian billionaire Vladimir Doronin, the ex-boyfriend of her mentor, British supermodel Naomi Campbell.

The 25-year-old Luo, who was crowned Miss Universe China in 2011, was photographed kissing and straddling the 43-year-old Doronin on the Spanish party island of Ibiza over the weekend. Doronin had only recently split from Campbell, 42, who earlier this year mentored Luo on her reality modeling TV show, The Face, in which Luo was named runner-up as a member of Team Naomi.

Neal Hamil, president of MIX Model Management NYC, has confirmed that Luo's contract has been ended due to "ongoing unprofessional conduct and unacceptable work ethic."

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A source told the UK's Daily Mail: "It's fair to say that Luo and Vlad met through Naomi. It's really unprofessional of Luo and it's not great behavior on Vlad's behalf."

Luo has angrily denied that she is dating Doronin, tweeting: "No, I'm not dating Vlad, No, I'm not his 'side chick,' no, didn't f**k, No, I'm not an escort, nor have I ever been."

Doronin is still married to his Russian wife Ekaterina with whom he has a teenage daughter.

Luo has been a model since high school. She was named runner up of an international modeling contest in Shanghai in 2003 and came in fourth place in a TV modeling contest hosted by national broadcaster CCTV in 2004. She was named the fourth runner-up in the 2011 Miss Universe contest pageant held in Sao Paulo, Brazil