At least 25 people were killed and about 100 others missing in the southern Philippines on Thursday after a landslide struck a community of gold prospectors, officials said.

The landslip hit a remote mountain community on Mindanao island that was declared off-limits last year due to the ever-present danger of landslides, but migrants in search of instant riches had ignored the warning, they added.

Rescuers using only spades and other hand tools pulled 25 bodies and 15 injured residents from the rubble after the landslide in Napnapan near Pantukan town at dawn, civil defence chief Benito Ramos told AFP.

"A military unit is in the area but they are basically digging with their hands," he told AFP.

Local military official Colonel Lyndon Paniza, who is coordinating the rescue from Pantukan, about two hours away via rugged mountain roads, said rescuers fear there could be more fatalities.

"We expect many were killed since the worst-hit was the middle, where there are more than 50 shanties," Paniza told AFP.

The landslide buried an area measuring about 7,500 square metres (81,000 square feet) as people slept, Paniza added.

Provincial governor Arturo Uy said more than 100 people were believed to be still buried under the collapsed mountainside.

Ramos however said the number of missing was an estimate based on figures from village officials.

The provincial government and local mining firms have been asked to bring heavy equipment up to the village to help local troops speed up the rescue.

The area had been hit by rains unleashed from a storm off Mindanao's southeast coast, the state weather service said.

Pantukan and nearby Monkayo town have drawn thousands of gold prospectors for years, and the largely unregulated mining activities have made the mountainside unstable and caused a series of deadly accidents.

Paniza said another landslide had occurred about two kilometres (just over a mile) away on April 22 last year.

Local officials said that landslide had killed 14 people, while another in 2009 killed 26.

Acting on the advice of national government geologists, local officials ordered all Pantukan gold rush areas evacuated last year.

However, they said some people had returned, possibly joined by new migrants drawn by stratospheric gold prices.

"These are small-scale miners who tunnel into the side of the mountains like rats," Ramos told AFP.

"This had been declared a no-man's-land, where people are forbidden to live. Local officials must explain why people are still there despite the national government's warning," Ramos told a news conference later.

"It's obvious that the gold attracts them. We cannot guard the mountain 24/7 because we have other responsibilities," he said.

The military is fighting a decades-long insurgency in the region and officials say rebels also extort money from the gold prospectors to finance the rebellion.

Provincial governor Uy said the local government had forcibly evacuated the residents after last year's landslide, when the town council passed an ordinance declaring the gold rush areas "no-habitation" zones.

"But the area is remote and the local government has difficulty monitoring the area," he told GMA television.

Miners had been warned previously of the danger, said environment and natural resources secretary Ramon Paje.

"We have identified this area as highly susceptible to landslides," he told ABS-CBN television in an interview.

"We had already told them even before the April incident happened that the top of the ridge is cracked, and it was just a matter of time" before another landslide struck, Paje added.

Ramos said two military helicopters were airlifting more rescuers to Pantukan from the southern port of Cagayan de Oro, one of two Mindanao cities hit hard by flash floods last month that killed more than 1,200 people.