A strong undersea earthquake struck off eastern Indonesia on Thursday, briefly triggering a tsunami alert, the country's meteorological and geophysics agency said.

Indonesian scientists gave the quake a preliminary magnitude of 6.5. The United States Geological Survey said its initial estimate was a more modest 5.5. Such discrepancies are common in the immediate aftermath of a quake.

There were no immediate reports of damage as a result of the quake 100 miles southeast of Sumbawa island, said Muhammmad Yusuf, a scientist at the meteorological and geophysics agency.

The agency initially said the quake had the potential to cause a tsunami and issued a warning to coastal towns close to the epicenter. It lifted the warning an hour later, saying no waves had hit shorelines.

Indonesia, the world's largest archipelago, is prone to seismic upheaval due to its location on the so-called Pacific "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin.

In December 2004, a massive earthquake struck off Sumatra island and triggered a tsunami that killed more than 230,000 people in a dozen countries, including 160,000 people in Indonesia's westernmost province of Aceh alone. A tsunami off Java island last year killed nearly 5,000.

Indonesia does not have a system in place to measure changes in sea level after an undersea earthquake so cannot say for sure whether a tsunami has been triggered. It issues a precautionary warning each time a quake with a preliminary magnitude of 6.5 strikes undersea.