A strong 6.0-magnitude earthquake has struck western Indonesia but no tsunami warning has been issued and there are no immediate reports of casualties or damage.

The quake struck at 4:39pm Saturday (1939 AEST) at a depth of 30 kilometres, 88 kilometres southeast of Sinabang, on the small island of Simeulue, the US Geological Survey said.

Diana Rahyu, an official from Indonesia’s meteorology, climatology and geophysics agency, said the quake was felt in parts of Sumatra, a huge island to the west of Simeulue.

But she added: “There is no threat of a tsunami … Until now, there are no reports of casualties or damage.”

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