Jakarta - An undersea earthquake registering 6.4 on the Richter scale struck off Indonesia's north Sulawesi province Sunday afternoon, but there were no immediate reports of injury or damage, the governmental seismology agency said.

The quake struck at 4:08 pm Jakarta time (0908 GMT) with an epicentre about 91 kilometres south-west of Gorontalo on Sulawesi, Indonesia's National Meteorology and Geophysics Agency said. It occurred at about 32 kilometres below sea level.

Indonesia, the world's largest archipelago nation, sits atop the Pacific Ocean's Ring of Fire, where the meeting of continental plates causes high volcanic and seismic activity. (dpa)