Survivors of a deadly quake in the Philippines begged rescuers Wednesday to keep searching for dozens of people buried in landslides, but officials said hopes of finding them alive were dim.

Two days after a 6.7-magnitude quake flattened homes, destroyed bridges and crumbled mountainsides on the central island of Negros, rescue workers battled without heavy equipment to dig through rubble in the search for the missing.

"Please do not give up, please continue searching," 47-year-old housewife Virginsita Magalso sobbed, her face streaked with dirt, as rescuers picked through mounds of dirt that covered the homes of family and friends.

"We can still save them, miracles happen all the time."

Magalso said her 68-year-old mother, an older brother, his wife, and their two young children were among those buried when part of a hill collapsed on homes in the farming community of La Libertad on Negros.

Magalso's house was further down the slope, sparing her direct family certain death, she said.

The official death toll from Monday's quake was 26, with 71 others missing from farming communities that had been engulfed by landslides in La Libertad and the nearby city of Guihulngan.

"Rescue teams have so far not seen or heard any signs of life underneath," Guihulngan mayor Ernesto Reyes told AFP, adding 29 people were believed buried in one disaster-hit village.

"None of our missing have so far been retrieved."

Reyes said the mountain village in Guihulngan was buried under about 10 metres (30 feet) of debris, with rescue efforts painfully slow because people had only picks, shovels and their bare hands to claw through the dirt.

Roads and bridges to Guihulngan, a coastal city of about 100,000 flanked by mountains, were badly damaged in the quake, meaning rescuers had difficulties bringing in earth movers and supplies for survivors.

"Our immediate concern now is how to serve the living. We don't have enough food, there is no electricity and water," Reyes said.

"We are appealing for help from everyone."

Civil defence chief Benito Ramos said in Manila that five military battalions, or about 2,000 troops, had been deployed to the devastated zones and were helping local rescue units.

"We are racing against time, and hoping against hope that maybe, just maybe some of them might still be alive," he said.

At least two mechanical diggers (backhoes) and several chainsaws and drills had reached La Libertad by noon Wednesday, but other areas remained cut off, according to Ramos.

Roel Degamo, the governor of Negros Oriental province where the worst of the damage occurred, said the likelihood of finding anyone alive was very low.

"We are in a state of shock, and all we can do now for those still missing is to pray," Degamo told AFP.

He said soldiers and rescuers in La Libertad raced on Tuesday to find a young woman who had sent a mobile phone text message to her relatives that she was pinned down, but alive.

The search, however, ended in tears hours later.

"She was found dead and still clutching her cell phone," Degamo said.

The regional military commander with responsibility for the disaster zone, Colonel Francisco Patrimonio, reported on Tuesday that 48 people had died, and another 92 were missing.

But the army said in a statement on Wednesday that the confirmed number of deaths was just 26, blaming initial confusion in the quake-hit areas for the change in numbers.

The revised tally matches figures from the National Disaster Risk Reduction and Management Council, the overall emergency response agency.