Unlike countries devastated by the huge wave, the military base on Diego Garcia was alerted by America's tsunami warning centre on Hawaii in the Pacific .

The base - officially called the British Indian Ocean Territory and described by the American military as the "best-kept secret in the navy" - was warned because it is linked to the US Pacific Command, according to American officials.

A spokesman for the Ministry of Defence in London insisted that British military personnel on the island received "no advance warning" of the tsunami. British forces were first alerted to the earthquake via the internet, he added.

A spokesman for the US national weather service confirmed to the Guardian that the Hawaii centre, part of America's National Oceanic and Atmospheric Administration (NOAA) had alerted the Diego Garcia base. He did not know if American military personnel at the base alerted anyone else in the region to the danger.

According to the base website: "Personnel on board Naval Support Facility Diego Garcia in the Indian Ocean are safe following the earthquake and subsequent tsunami that had devastating effects on south-east Asia. Facilities and operations were not affected." An NOAA log shows that the US Pacific Command, including Diego Garcia, was given a specific warning about the tsunami some two and three quarter hours after the earthquake. This was shortly after the tsunami had struck Sri Lanka and well after it hit Indonesia and Thailand. It gave Diego Garcia advance warning of about an hour.

But, ironically, the one community which received a warning did not need it. As the base website put it: "Favourable ocean topography minimised the tsunami's impact" on the Chagos archipelago of which Diego Garcia is a part. The atoll is just to the west of one of the deepest parts of the Indian Ocean.

Professor Michel Chossudovsky of Ottawa University said the argument put forward by other experts that countries hit by the tsunami could not have been warned of the approaching waves because they had no sensors or special buoys in the Indian Ocean was a "red herring".

Prof Chossudovsky, who helps run the centre for research on globalisation, added: "We are not dealing with information based on ocean sensors. The emergency warning was transmitted in the immediate wake of the earthquake based on seismic data." With modern communications,"the information of an impending disaster could have been sent round the world in a matter of minutes, by email, by telephone, by fax, not to mention by satellite television", he said.

He said the US military had advanced systems "which enables it to monitor in a very precise way the movement of the seismic wave in real time".