A strong earthquake struck deep under the sea in eastern Indonesia yesterday, but there were no immediate reports of damage or injuries, officials said.

The earthquake of a preliminary magnitude of 6.0 struck on the fifth anniversary of another quake that spawned the Asian tsunami that left 230,000 people dead in a dozen countries around the Indian Ocean rim.

The Boxing Day 2004 tsunami was sparked by a 9.2-magnitude underwater quake off the Indonesian island of Sumatra.

Yesterday's quake was at a depth of 35 miles, too far below the earth's surface to cause a tsunami, said Indonesian Meteorology and Geophysics Agency seismologist Paulus Prihandoyo.

The quake had its epicentre about 165 miles north of Saumlaki and about 1,680 miles east of the capital Jakarta, the US Geological Survey said.

Residents in Saumlaki said the quake panicked people and caused an electricity blackout, but there were no reports of damage or injuries.

Indonesia sits above a series of fault lines that make the vast island nation one of the most earthquake-prone places in the world.

A magnitude 7.6 earthquake struck off West Sumatra on September 30 and killed hundreds of people and toppled hundreds of homes and buildings.

To mark the anniversary of the 2004 tsunami, Buddhist monks chanted on white-sand beaches in Thailand and thousands prayed at mosques in Indonesia.

In Thailand, hundreds of residents and foreigners returned to the beaches on the island of Phuket to recall one of the worst natural disasters of modern times.

A moment of silence was observed on Phuket's Patong Beach, a popular strip of hotels and restaurants, to mark the moment the tsunami struck.

Buddhist monks in bright orange robes chanted prayers. Onlookers wept and embraced.

Giorgio Capriccioli, an Italian who lives on Phuket, carried a bouquet of white flowers into the ocean.

He waded knee-deep in water that five years ago was clogged with corpses and cast the flowers adrift to honour the memory of two friends. His wife owns several beach-front shops but decided not to go to work the morning the tsunami struck.