JAKARTA (AFP) - A powerful 6.3-magnitude earthquake struck eastern Indonesia on Wednesday, US seismologists said, but no tsunami warning was issued and there were no immediate reports of damage or casualties.

The quake struck at a depth of 52km under the Molucca Sea at about 3.40pm, between the islands of Sulawesi and Halmahera, the US Geological Survey said.

Mr Mochammad Riyadi, a senior official from Indonesia's meteorology, climatology and geophysics agency, said the quake was felt strongly on Halmahera, which is part of the Maluku Island chain.

However he added there were no immediate reports of casualties or damage and no tsunami alert was issued.

Indonesia sits on the Pacific "Ring of Fire" where tectonic plates collide, causing frequent seismic and volcanic activity.