Super typhoon Mangkhut is now swirling towards Hong Kong and the Chinese coast.

It's gaining in strength over the South China Sea after hurtling through the Philippines, where it wreaked havoc that killed at least 28 people.

Tropical cyclone Mangkhut is the strongest to hit the region this year, with gale force winds of more than 200 kilometres an hour, equivalent to a maximum Category 5 "intense hurricane" in the Atlantic.

Philippines officials say the death toll has risen largely because of landslides in northern mountain provinces and at least 13 people are missing.

Mangkhut is expected to skirt 100 kilometres south of Hong Kong and veer west towards the coast of China's southern Guangdong province.

Hong Kong has raised its highest No. 10 typhoon signal, as fierce waves pound low-lying areas and strong winds rattle windows in many towering skyscrapers.

Some residents have been evacuated from low-lying areas with storm surges of up to 3.5 metres expected.