MEDAN, Indonesia -- Twelve women working in an illegal gold mine in Indonesia's North Sumatra province were killed when a cliff collapsed and triggered a landslide that buried them, police said.

Unlicensed mines are common across mineral-rich Indonesia, with abandoned sites attracting locals who scrounge for leftover gold ore without using proper safety equipment.

A collapsed cliff in North Sumatra's Mandailing Natal district struck Thursday afternoon, killing 12 women -- aged 30 to 55 years old -- who were digging for gold in an abandoned illegal mine.

"The cliff around the mine collapsed and buried the 12 women, killing them all," local police chief Marlon Rajagukguk told AFP late Thursday, adding that the victims were not professional miners.

Two other women who worked alongside them managed to survive the disaster and ran back to the village to report the incident to the authorities.

It took hours for rescuers to evacuate the victims' bodies as they were in a two-metre deep hole, which was filled with mud.

"Now all the bodies of the victims have been returned to their family," Rajagukguk said.

Illegal gold mining is rampant in the Mandailing Natal, about 300 km (186 miles) south of the provincial capital of Medan, and several sites are abandoned by the operators.

Mining accidents are frequent across the archipelago due to landslides, especially during the monsoon summer months.

Last year six miners died when an illegal gold mine collapsed in Parigi Moutong on the island of Sulawesi.

In 2020, 11 miners in Sumatra were killed in a landslide triggered by heavy rains.