By Avril Ormsby

LONDON (Reuters) - Sports fans attending the London Olympics were told by Olympic bosses on Sunday to avoid sending non-urgent text messages and tweets during events because an overloaded network was affecting television coverage.

Coverage of the men's road cycling race on Saturday left many viewers in the dark at times, including details on how far back the chasing pack was from the leaders. Commentators were unable to get timing information due to issues surrounding the communications network of the GPS satellite navigation system.

It was particularly annoying for the home crowd, who had tuned into to watch what had been billed as one of Britain's best chances of winning an early gold medal with sprint king Mark Cavendish.

Many vented their anger on Twitter at the lack of information - and their disappointment at Cavendish's eventual defeat.

An International Olympic Committee spokesman said it was a network issue, caused by hundreds of thousands of fans, who had lined the streets of London to cheer the British team on, sending messages. He urged people to spread their use.

"Of course, if you want to send something, we are not going to say 'don't, you can't do it', and we would certainly never prevent people," the IOC spokesman said.

"It's just, if it's not an urgent, urgent one, please kind of take it easy.

"We don't want people to stop engaging in social media but we are asking to see if people can send by other means."

The use of mobile phones to access the Internet and take and send photos and video has exploded in recent years, making London 2012 the really first social media Games, but also putting extra pressure on the networks.

Mayor of London Boris Johnson warned last year the networks would face a "massive strain", with hundreds of thousands of spectators wanting to share a moment of victory or defeat with friends and family.

At the time he said a huge amount of work was being done to make sure there was enough coverage, and that mobile operators and infrastructure companies would "crack it" in time.

Enough cable has been laid in the Olympic Park in east London to stretch between London and New York, suggesting that if there were any problems, they would be more likely to occur at venues outside the park.

Television coverage is being carried out by the Olympic Broadcasting Services, created by the International Olympic Committee in 2001 to ensure uniform coverage at all Games.

The IOC spokesman said it appeared the problem lay with oversubscription on one particular network, and talks had taken place late Saturday and early Sunday in attempt to share more of the data.

"We are taking action on a number of things," the spokesman said.

"It's mainly a technical issue with the network. It's a network issue, and it is that which we are working on."

He conceded though that asking people to not send messages at critical moments, may not have "an awful lot of effect".

(Editing by Alison Williams)