A typhoon weakened as it cut across the Philippines on Monday with strong wind felling trees and power lines, and authorities warned of flash floods and mudslides but there were no official reports of casualties.

Typhoon Nock-ten, locally known as Nina, weakened to 150 kph (93 mph) as it headed west towards provinces south of the capital Manila, picking up speed to 20 kph.

A storm alert was in place and land, sea and air transport were all suspended as authorities told the public to take precautions and prepare for strong wind and heavy rain.

The Philippines is one of the world's worst-affected countries when it comes to typhoons, with an average of 20 a year passing or hitting the archipelago of more than 7,000 islands.

Tens of thousands of people in the predominantly Christian country spent Christmas in shelters after authorities moved them to safety on higher ground.

Emergency workers were mobilised to clear roads of debris, like fallen trees and power lines in the coconut-growing region, with some central areas plunged into darkness.

The typhoon was due to make a fifth landfall in Batangas on Monday then move towards Manila after its arrival in the country at Catanduanes province on Sunday evening.

Ricardo Jalad, head of the national disaster risk reduction management council, said there were no reports of deaths or missing people but communications were disrupted.

"We expect to get reports from the field as soon as power and telephone services are restored," Jalad said.

Radio DZBB reported a boy was killed in Quezon province when he was pinned down by a coconut tree and another girl injured in Camarines Sur when a house collapsed. The reports could not be immediately verified.