At least 66 people have been killed while hundreds of thousands fled their homes as one of the strongest typhoons this year ripped through the central Philippines, authorities say.

Typhoon Kalmaegi has flooded entire towns on the most populated central island of Cebu, where 49 of the fatalities were located. Twenty-six others are missing, a civil defence official said in a radio interview on Wednesday.

Videos show people sheltering on rooftops, while cars and shipping containers have been swept through the streets.

The official death toll includes six crew members of a military helicopter that crashed on Mindanao island, south of Cebu, after it was deployed to assist in relief efforts.

The aircraft went down on Tuesday near Agusan del Sur and was one of four sent to help.

Communication with the helicopter was lost, which immediately prompted the launch of a search and rescue operation, the Philippine Air Force said. Later, a spokeswoman said six bodies had been recovered, believed to be those of the pilot and crew.

The typhoon, locally named Tino, has weakened since making landfall early on Tuesday but has continued to bring winds of more than 80 mph (130 km/h).

It is forecast to move across the Visayas islands region and out over the South China Sea by Wednesday.

Rafaelito Alejandro, the deputy administrator at the Office of Civil Defence, provided the updated casualty numbers during an interview on local radio station DZMM on Wednesday.

Rescuers are waiting for the skies to clear before they can deliver aid, as debris and vehicles block the roads. Cebu provincial governor Pamela Baricuatro has declared a state of calamity to facilitate disaster relief efforts.

The situation in Cebu is really unprecedented, she stated, underscoring the dangers posed by flooding rather than the winds. Most of the deaths have been attributed to drowning, as the storm sent torrents of muddy water into towns.

Damage to residential areas on Cebu has been extensive, compelling rescue teams to use boats to reach those trapped in their homes.

More than 400,000 people have been displaced by the devastation, according to a report by the national disaster agency, signaling an ongoing humanitarian crisis.

The Philippines typically experiences around 20 storms and typhoons each year. The latest disaster comes on the heels of recent typhoons that also inflicted casualties and infrastructure damage.

Typhoon Kalmaegi is forecast to head towards Vietnam, which is already experiencing record-breaking rainfall.