Villagers were digging for gold in the remote Solok district on Sumatra - one of Indonesia's western islands - when disaster struck.

Mud plunged down the surrounding hills and buried them, Irwan Effendoi, head of the local disaster mitigation agency office, said.

He said at least 25 people were still buried.

Three people were pulled out alive with injuries by rescuers.

Search efforts in the worst-affected area, near Nagari Sungai Abu village, were hampered by mudslides that covered much of the area, blackouts and lack of telecommunications.

"The devastated mining area can only be reached by walking for four hours from the nearest settlement," said Ilham Wahab, the agency's spokesperson.

Informal mining operations are common in Indonesia, providing a tenuous livelihood to thousands who labour in conditions with a high risk of serious injury or death.

Landslides, flooding and tunnel collapses are just some of the hazards facing miners.

Much of gold ore processing involves highly toxic mercury and cyanide, and workers frequently use little or no protection.

Several major landslides have already hit Indonesia this year, killing dozens, including two such incidents in Sumatra.

At least 43 people were killed when flash flooding led to mudslides and a deluge of cold lava through mountainside villages on the island in May.

Two months earlier, heavy rains triggered flash floods and a landslide in West Sumatra, killing at least 26 people and leaving 11 others missing.

Meanwhile, in April, at least 14 people died and three were reported missing after landslides on the central island of Sulawesi.