Mobile phone networks face a massive strain during next summer's Olympics as sports fans rush to send pictures and messages, Mayor of London Boris Johnson warned on Thursday.

The use of mobile phones to access the internet and take and send photos and video has exploded in recent years, and is expected to be in high demand during the 2012 London Games, putting pressure on the networks.

A potential overload was a concern of Johnson's two years ago, he said, before adding that he was confident mobile operators and infrastructure companies would crack it.

There is a huge amount of work going on at the moment to make sure that we have enough coverage, he told reporters on the fringes of an Olympic conference aimed at promoting business opportunities for small-and-medium sized businesses.

We have got to be realistic, and in the 100 meters final or whatever it happens to be, people will want to download huge quantities all over the world, they will want to be sending huge quantities of data in JPEG (format) or film or whatever, and that will place massive strain on the network.

It will not only be sports fans who will be looking to send messages during events, but transport and emergency services use mobile phones to a great extent, so any clogging of the system could be damaging.

During the July 7 attacks on London's transport system, police shut down a major mobile phone network to the public in part of the capital, restricting it to members of the emergency services with special handsets.

Johnson said the need for planning permission to put up masts, or mobile phone towers, had held up some installations, including on the Olympic Park in Stratford, east London, but he was confident future applications would be successful.

One of the things that we are doing is working with the mobile phone companies to install enough masts around the park ... to make sure we have enough physical infrastructure, enough coverage for the huge demands there is going to be on communications, he said.

I'm confident people will be able to use their machines in a very free way.

(Reporting by Avril Ormsby; editing by Stefano Ambrogi)

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