The death toll from a strong earthquake that struck central Indonesia at the weekend has risen to six, an official said Tuesday, after rescuers reached villages that had been cut off by a landslide.

"Six people have died, including a nine-year-old boy, and 43 are injured. More than 400 homes are now damaged," National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho told AFP.

"There is still an area that we haven't accessed, so we'll send two helicopters there to distribute aid and assess the damage there. It's possible the death toll could rise, but we're hoping for the best."

The 6.3-magnitude struck the island of Sulawesi Saturday evening at a depth of around 20 kilometres (12 miles), the US Geological Survey said, close to villages in the districts of Parigi Moutong and Sigi.

Landslides had blocked access to 14 villages in surrounding districts, and 300 soldiers and heavy equipment, including bulldozers, had been deployed to remove the debris, Sutopo said.

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