Typhoon Usagi closed in on Hong Kong, threatening to severely disrupt life in the Asian financial hub, shutting down one of the world's busiest sea ports and forcing hundreds of flight cancellations.

Usagi, the strongest storm to hit the Western Pacific this year, left at least two dead in its trail as it triggered heavy rains, flooding and landslides in the Philippines and Taiwan.

Usagi, the strongest storm to pulverize the city in more than three decades, is expected to make landfall soon.

The typhoon, which packed winds of 165 kilometres (103 miles) per hour and triggered a No 3 signal warning from the Hong Kong observatory, is feared to throw life in China's Pearl River Delta into disarray.

"At 1 pm, Severe Typhoon Usagi was estimated to be about 300 kilometres east of Hong Kong (near 22.1 degrees north 117.1 degrees east) and is forecast to move west-northwest at about 20 kilometres per hour across the northeastern part of the South China Sea and towards the vicinity of the Pearl River Estuary" the Hong Kong Observatory said in its latest release.

Chian's official Xinhua news agency reported that the country's top weather bureau issued the red alert, its highest warning, saying that Usagi, which means "Rabbit" in Japanese, could bring gales and rains to southern coastal areas.

The "19th super typhoon" has forced evacuation of more than 80,000 people in Fujian province, China's National Meteorological Centre said, adding that the provinvial goverment has already deployed at least 50,000 relief workers.

Flight schedules of the major regional airliners were thrown into disarray, with Cathay Pacific Airways and Hong Kong Dragon Airlines cancelling all flights into and out of the city's airport from 6 pm (6 am EDT) on Sunday.

As many as 376 flights will be cancelled by Cathay and other airlines, the Agence France-Presse reported, citing Hong Kong's airport authority.