At least 46 people have died after Typhoon Kalmaegi unleashed heavy rains and floods across the central Philippines, trapping people on their roofs and submerging cars, officials say.

The dead included six crew members of a military Huey helicopter, which crashed on the island of Mindanao, where it was carrying out a humanitarian disaster response mission, according to the military.

Although the powerful storm, locally named Tino, has weakened since it made landfall early on Tuesday, it has continued to lash the country with sustained winds of 87mph and gusts of up to 121mph.

Tens of thousands of people have been evacuated across the Visayas islands, the national disaster agency reported.

Several people were trapped on their roofs by floodwaters in the coastal town of Liloan in Cebu, said Gwendolyn Pang, secretary-general of the Philippine Red Cross.

She said in the city of Mandaune, also in Cebu, floodwaters were “up to the level of heads of people”, adding that several cars were submerged in floods or floated in another community in Cebu.

“We have received so many calls from people asking us to rescue them from roofs and from their houses, but it’s impossible,” Ms Pang said. “There is so much debris, you see cars floating, so we have to wait for the flood to subside.”

Fierce winds either ripped off roofs or damaged around 300 mostly rural shanties on the island community of Homonhon in Eastern Samar, but there were no reported deaths or injuries, mayor Annaliza Gonzales Kwan said.

“There was no flooding at all, but just strong wind,” she said. “We’re okay. We’ll make this through. We’ve been through a lot, and bigger than this.”

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Warning of ‘life-threatening storm surges’

The combination of Kalmaegi and a shear line brought heavy rains and strong winds across the Visayas and nearby areas, state weather agency PAGASA said. A shear line is the boundary between two different air masses such as warm and cold air.

More than 180 flights to and from the affected areas have been cancelled, while those at sea were advised to head to the nearest safe harbour immediately and remain in port.

PAGASA warned of a high risk of “life-threatening and damaging storm surges” that could reach more than three metres high along coastal and low-lying communities in the central Philippines.

Vietnam gears up for storm

The Vietnamese government has said it was preparing for the worst-case scenario as it braced for the impact of Kalmaegi.

The typhoon is forecast to make landfall in Vietnam’s central regions on Thursday night. Those areas have already suffered heavy floods which killed at least 40 people and left six missing over the last week.

“This is a very strong typhoon, which continues to strengthen after entering the East Sea,” the government said in a statement, referring to the South China Sea.

Kalmaegi hit the Philippines as it continues to recover from several disasters, including earthquakes and severe weather over recent months.

Around 20 typhoons and storms hit the Philippines each year, and the country is also often struck by earthquakes and has more than a dozen active volcanoes.