Storm now moving towards China’s heavily populated southern coast with winds of more than 140km/h

The death toll from Typhoon Mangkut has risen to 25 in the Philippines after the storm unleashed ferocious winds and rain that flattened homes and crops, damaged airports and forced tens of thousands to flee.

Presidential adviser Francis Tolentino said the central northern mountainous region of Cordillera appeared worst hit, with 20 confirmed dead, followed by four in Nueva Ecija and one in Marikina. However, the figures do not include Cagayan, where the storm first made landfall.

The storm is now heading towards China’s heavily populated southern coast at a speed of about 30km/h. Hundreds of flights have been cancelled in Hong Kong and China’s National Meteorological Centre has issued a red alert for the typhoon – the highest possible alert.

On Sunday morning it was carrying sustained winds of 145km/h and gusts of up to 180km/h after leaving the Philippines.

Earlier, Tolentino said the dead included an infant and another child who were among four people killed in a landslide in Nueva Vizcaya, one of several provinces battered by the typhoon on Saturday. At least two emergency workers have been killed in landslides.

About 90,000 people were evacuated from high-risk areas and told not to return home until the danger has passed.

Ricardo Jalad, the civil defence chief, said the initial casualties were reported from the mountainous Cordillera region, adding that there were already 41 incidents of landslides reported in the region and that the death toll would rise.

Survivors were traumatised by the confrontation with the monster storm. “It felt like the end of the world ... that was stronger than Lawin”, said Bebeth Saquing, 64, using the local name for Super Typhoon Haima, which was one of the most powerful storms of 2016.

In Baggao town in Cagayan where the typhoon made landfall early on Saturday, three power towers had been brought down, the defence secretary, Delfin Lorenzana, said. Television reports showed how the typhoon ripped off roofs and destroyed farms. Emergency workers are repairing Tuguegarao airport in northern Cagayan province after it was left inoperable.

The government warned of storm surges of up to six metres as well as massive flooding and landslides as downpours caused rivers to overflow. Several dams have been opened to release water, prompting more warnings of flooding especially in central Luzon, a natural catchment area that produces the most rice in the country.

More than five million people were estimated to be at risk from the storm, which the Hawaii-based Joint Typhoon Warning Center earlier categorised as a super typhoon with gusts equivalent to a category 5 Atlantic hurricane. In Cagayan’s capital city of Tuguegarao, tin roofs and other debris hurtled through the air and store signs crashed to the ground.

With a rain cloud band 900km wide, combined with seasonal monsoon rains, there are still fears the typhoon could trigger fresh landslides and flash floods. Storm warnings were raised in 25 provinces across Luzon, restricting sea and air travel.

Ricardo Jalad, the country’s civil defence chief, earlier told an emergency meeting led by the president, Rodrigo Duterte, that about 4.2 million people were vulnerable to the most destructive effects near the typhoon’s 125km eye. Nearly 48,000 houses in those high-risk areas are made of light materials and vulnerable to Mangkhut’s winds.

Ninia Grace Abedes from Cagayanabandoned her bamboo hut and took her four children to a school building serving as an emergency shelter. The 33-year-old said the 2016 typhoon blew away their hut, which they abandoned before the storm hit. “If we didn’t, all of us would be dead,” Abedes said.

Duterte, who cancelled his appearance at a missile test firing aboard a navy ship off northern Bataan province, has asked cabinet officials from the north to help oversee disaster response work if needed, but said it was too early to consider seeking foreign aid. “It would depend on the severity of the crisis,” Duterte said. “If it flattens everything, maybe we need to have some help.”

The typhoon came at the start of the rice and corn harvesting season in Cagayan, a major agricultural producer, and farmers scrambled to save what they could of their crops.

On Guam, where Mangkhut passed, residents dealt with flooded streets, downed trees and widespread power outages. About 80% of the US territory lost power but it was restored by Thursday morning.

Facebook Twitter Pinterest Strong winds and rain batter buildings in Tuguegarao city. Photograph: Aaron Favila/AP

Mangkhut, a Thai word for the mangosteen fruit, is the 15th storm this year to batter the Philippines, which is hit by about 20 a year and is considered one of the world’s most disaster-prone countries.

This story contains material from the Associated Press and Agence France-Presse