JAKARTA: A strong 6.6-magnitude earthquake hit Indonesia's Molucca Sea on Wednesday (Mar 18), the US Geological Survey said, but no tsunami alert was issued and there were no reports of damage.

The quake struck at a depth of 41km, 134km northwest of Kota Ternate at 6.12am Singapore time, the USGS said. The Pacific Tsunami Warning Center said there was no tsunami threat.

Hendra Rahman, an official from Indonesia's meteorology, climatology and geophysics agency, said the quake was felt moderately in Manado, on Sulawesi island, and on the island of Ternate. But he added there had been no reports of damage.

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

A huge undersea quake in 2004 triggered a tsunami that killed more than 170,000 people in Aceh province, on western Sumatra island, and tens of thousands more in other countries with coasts on the Indian Ocean.