HONG KONG - Police are investigating the case of an obscene photo featuring pop stars Gillian Chung and Edison Chen that is circulating on the Internet.

The digitally faked picture shows the two, both 27, side by side in bed. The woman is wearing a bikini top and little else.

Reports said the image was posted on the Web on Monday and had spread to several of Hong Kong's online forums by yesterday.

A computer-modified photo showing Chen and his ex-girlfriend - former artiste Bobo Chan, 28 - in a sexual situation also found its way to the Internet yesterday.

Chung's label, Emperor Entertainment, said in a statement yesterday that it had found a fake picture of the singer-actress on the Web and reported the incident to the police,

'We have already passed the case to lawyers to follow up. If the distributor or upload person is confirmed, we will seek court action,' it added.

Chen said through his lawyer that the photos were an 'irresponsible practical joke', though he did not specify if they were fake. He added that he may take legal action.

In 2006, Easy Finder magazine sparked a furore when it published stealth photos of Chung, one half of girl group Twins, changing backstage at a concert.

The Canadian-born Chen has been linked to stars including actress Maggie Q and Chung since he entered showbiz in 2000. He is dating Vincy Yeung, the niece of Emperor chairman Albert Yeung.