JAKARTA : A 5.6-magnitude earthquake struck off Indonesia's Sumatra island on Saturday, but there was no threat of a tsunami and no immediate word of damage, a meteorologist said.

The earthquake, which hit at 14:17 hours (0717 GMT), occurred at sea about 137 kilometres (82 miles) northwest of the city of Bengkulu, according to a statement from Indonesia's Meteorological and Geophysics Agency.

"A tsunami alert was not issued and there are no reports of damage so far," agency staff member Ali Imron told AFP.

The quake struck at a depth of 29 kilometres.

Bengkulu province was badly damaged in an 8.4-magnitude quake in September that struck off Sumatra's west coast, killing 23 people.

It was followed by a series of major aftershocks.

The Indonesian archipelago sits on the Pacific Ring of Fire, where continental plates meet and cause frequent seismic and volcanic activity.

Indonesia was the nation worst hit by the earthquake-triggered Asian tsunami in December 2004, which killed some 168,000 people in Aceh province. - AFP/ch