Helicopters on Tuesday dropped the first food and emergency supplies to a remote mountainous area three days after a deadly earthquake rocked a north Indonesian island and triggered landslides that cut off villages, a disaster official said.

"Many victims remain beyond reach," said Sutopo Purwo Nugroho of the Disaster Management Agency, adding that rescuers were also being hampered by downed communications. "They are isolated from the outside world after earthquake-triggered landslides."

The magnitude-6.3 quake struck Saturday evening near Palu city on Sulawesi Island as residents were ending their fast for the Muslim holy month of Ramadan. Six people were killed, and at least 43 others were injured.

More than 300 soldiers were deployed to rural Lindu sub-district to help clear roads into Lore Lindu National Park that were blocked by quake-triggered landslides in more than 60 areas, Nugroho said.

Limited telephone communication was hampering rescue efforts, but helicopters were able to evacuate some injured victims from the isolated mountainous area, including two women with broken necks, he said.

Nearly 2,000 people were displaced by the quake, which destroyed roads, bridges and more than 470 homes and buildings in Parigi Mountong and Sigie, the closest districts to the epicenter.

Indonesia is prone to seismic upheaval due to its location on the Pacific "Ring of Fire," an arc of volcanos and fault lines around the Pacific Basin.

A giant quake off the country on Dec. 26, 2004, triggered a tsunami in the Indian Ocean that killed 230,000 people, half of them in Indonesia's westernmost province of Aceh.