JAKARTA - A MODERATE, 5.6-magnitude quake struck off Indonesia's northern Sulawesi island on Tuesday, seismologists said, but there were no immediate reports of damage or casualties.

The quake, which hit at 6.31pm (7.31 pm Singapore time), was centred at sea 43 kilometres south-east of Melonguane town in North Sulawesi province, the Indonesian geophysics agency said.

No tsunami warning was issued.

The Indonesian archipelago sits on the so-called Pacific Ring of Fire where continental plates meet, causing frequent seismic and volcanic activity. -- AFP