JAKARTA: A 6.4-magnitude earthquake struck off eastern Indonesia in the early hours of Monday, triggering a brief tsunami alert that was swiftly lifted, according to seismic monitoring organisations.

The quake struck deep at some 171 kilometres (106 miles) below the surface of the earth in the Banda Sea, the United States Geological Survey (USGS) said.

A tsunami alert was initially triggered by the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS).

However, IOTWMS followed up with a second bulletin that said there was "no threat to countries in the Indian Ocean".

The quake's epicentre was located in a sparsely inhabited part of the Banda Sea, 222 kilometres northwest from Indonesia's Tanimbar Islands and 380 kilometres from Ambon, the capital of Maluku province.

A similar 6.1-magnitude quake hit close to Monday's epicentre on 26 February and caused no damage.

Indonesia sits on the so-called Pacific Ring of Fire, a seismic activity hotspot. It is frequently hit by quakes, most of them harmless.

However, the archipelago remains acutely alert to tremors that might trigger tsunamis.

In 2004, a devastating tsunami triggered by a magnitude 9.3 undersea earthquake off the coast of Sumatra killed 220,000 people in countries around the Indian Ocean, including 168,000 in Indonesia.