Indonesia briefly issued a tsunami alert on Thursday after a strong earthquake rocked the east of the country.

The country's geophysics agency said the quake had a preliminary magnitude of 6.6, while the U.S. Geological Survey put the initial magnitude at 5.9.

The quake struck 170 miles southwest of the Maluku island chain at a depth of 6 miles.

The Indonesian agency initially put out a tsunami warning but retracted it after no waves came.

An official said there were no immediate reports of damage as a result of the quake.

Indonesia, the world's largest archipelago with a population of 235 million people, is prone to seismic upheaval because of its location on the "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin.

A magnitude-9 quake off Sumatra's coast in 2004 triggered a tsunami that killed more than 230,000 people in a dozen countries, most of them in Indonesia.