Image copyright Al Bello/Getty Image caption Rupert Murdoch is executive chairman of 21st Century Fox

Rupert Murdoch's film and media giant 21st Century Fox says it is cooperating with the European Commission after officials raided its Fox Network offices in London.

EC competition authorities are reported to have seized documents relating to sport media rights earlier on Tuesday.

Other companies involved in sports rights have also received what the EC called "unannounced inspections".

It is unclear which other companies were raided and when.

"The commission has concerns that the companies involved may have violated EU anti-trust rules that prohibit cartels and restrictive business practices," the European Commission said in a statement.

"Unannounced inspections are a preliminary step into suspected anti-competitive practices."

The statement said it "does not mean that the companies are guilty of anti-competitive behaviour, nor does it prejudge the outcome of the investigation itself".

Sports broadcasting has become a huge business in Europe and the US, with networks spending billions of pounds to secure exclusive rights to show games in top-flight leagues to attract viewers.

Fox Networks Group is an operating unit of Fox, which distributes TV and cable channels and content around the world.

"Fox Networks Group is cooperating fully with the EC inspection," a spokesman said.

The move comes amid a shake-up of Mr Murdoch's empire.

21st Century Fox has agreed to sell most of its entertainment assets, including its stake in Sky, to Disney for $52.4bn. But in February, US giant Comcast offered $31bn for Sky.

As part of the shake-up and deal with Disney, 21st Century is trying to buy the 61% of Sky it does not own, a proposal that has run into problems with the UK competition authorities.

The Commission said there was no legal deadline to complete inquiries into anti-competitive conduct and EC investigations can be lengthy.