Earthquake in Indonesia's Sumatra island

7.7 quake hits off Indonesia's Sumatra island; brief tsunami warnings issued.

A huge earthquake has struck the Indonesian island of Sumatra, triggering blackouts, widespread panic and tsunami warnings.

The 7.8 magnitude quake, the second major temblor to hit the island in six months struck at 5.15 am local time (2215 GMT) 125 miles off the city of Sibolga, on Sumatra's north west coast, which was devastated in the 2004 Indian Ocean tsunami.

Buildings shook and residents of coastal cities fled to higher ground, and there were blackouts in Medan and Banda Acheh. However there were no reports of major damage or casualties and the tsunami warnings issed by the Indonesian Government and Thailand were lifted two hours later.

Residents of Banda Aceh, the provincial capital, said they felt the earth shudder with frightening intensity for about a minute as the first earthquake was followed by three strong after-shocks.

Many fled their homes or piled onto motorcycles to head inland in fear of destructive waves .

"People panicked and ran out of the house, it lasted almost a minute," an AFP reporter in Banda Aceh said. "I saw a lot of people who live close to the sea using motorcycles to drive inland."

The US Geological Survey said the earthquake struck at a depth of 29 miles (46 km). The epicentre was 60 kilometres southeast of Sinabang, on Simeulue Island, the epicentre of the 2004 earthquake.

Officials in Sinabang and the Indonesian capital of Jakarta said there were no immediate reports of damage near the epicentre. "Our personnel haven't found any damage in Sinabang," local police chief Dedi Junaidi told MetroTV.

Indonesia sits on the so-called Pacific rim of fire, along which 90 per cent of the world's earthquakes and 80 per cent of the world's largest earthquakes occur.

Today’s earthquake comes six months after a 7.6 magnitude quake devastated the Sumatran city of Padang, 200 miles (350 km) to the south of Sibolga, killing 1000 people.

A massive 9.3 magnitude earthquake struck off the west coast of Sumatra in 2004, triggering the tsunami that inundated coastal communities in Indonesia and other countries in the Indian Ocean rim killing about 220,000 people, most of them in Aceh.

Geologists regularly warn that the Sumatra is due a massive earthquake that will be even bigger and more devastating than the 2004 tremor.