Hong Kong flag carrier Cathay Pacific said Saturday it would cancel all flights to and from the city, a day ahead of the anticipated arrival of Super Typhoon Usagi, the most powerful storm of the year.

Usagi, forecast to be closest to Hong Kong on Sunday and Monday, could pose a "severe threat" to the city, the Hong Kong Observatory said on its website.

Cathay Pacific flights in and out of the city will be cancelled from 6:00 pm (1000 GMT) Sunday, the airline said, adding that services will gradually resume on Monday "if weather conditions permit".

Dragonair, a sister airline, will halt flights for the same period.

Hong Kong's international airport will remain open, authorities told AFP.

Usagi, packing sustained winds of 240 kilometres per hour (150 miles per hour) with gusts of nearly 300 kilometres per hour, brought torrential rain and strong winds to the Philippines and Taiwan Saturday.