Major music labels have called on three Chinese-language web portals to stop providing music services because of copyright law infringement.

The International Federation of the Phonographic Industry (IFPI) told Sohu.com, Sina.com and Tom.com on Thursday to stop selling one-time listen services of mainly Mandarin and Cantonese pop hits.

It also told the sites to apologise to the companies and artists who owned the rights to the music, and pay them damages - or else face legal action.

The theme to the movie Titanic is a popular choice for users of the sites

The case highlights the growing problem for record labels as they try to keep track of where their artists' music is being made illegally available over the internet.

The situation is considered particularly bad in China and in 1999 a group of record companies sued sites based in the country for offering free music downloads without permission.

The service offered by the three sites allows people to pick songs from the internet and send them to a friend on their mobile phone.

Popular songs found on the sites include music by Hong Kong pop diva Faye Wong, Taiwanese boy band F4 and the theme song to the film Titanic.

Contract

In response to the IFPI's approach, Sohu.com shut down its music service the same day but suggested it might seek to resume the service.

In a statement, it said the threat of legal action had come as a "complete surprise" because it had a contract with a licensing agent to provide their service.

It added that the licensing agent had, in turn, a related contract with the China Music Copyright Association, a non-profit organisation.

As Sohu.com stopped its music service, rival Sina.com said it was considering ceasing its version of the so-called "song dedication" service.

Tom.com officials could not be reached for comment.

An industry spokesman in Beijing said he estimated the sites had made a combined $6.3m (�3.9m) over the past few months.

Negotiations

The sites have been giving web users access to around 1,100 tracks, about 90% of which were owned by IFPI member companies.

The IFPI, based in London, represents the music divisions of Sony AOL Time Warner, Vivendi Universal, EMI and Bertelsmann.

A Sohu spokeswoman said she doubted the accuracy of the amount of revenue quoted by the spokesman.

She added that the song service amounted to 0.3% of the portal's $6.1m (�3.8m) second-quarter revenue.

Nevertheless, Sohu stopped its service "pending the negotiations" with a law firm in Beijing hired by IFPI.