The year's most powerful typhoon has hit southern China, forcing hundreds of flight cancellations, shutting down shipping and putting a nuclear power plant on alert after pummelling parts of the Philippines and Taiwan with heavy rains and fierce winds.

Typhoon Usagi veered away from Hong Kong at the last minute and made landfall north-east of the former British colony. Forecasters had warned earlier that it posed a "severe threat" to the southern Chinese city.southern Chinese city.

Usagi – Japanese for rabbit – was classified as a severe typhoon, with sustained winds of 109mph (175km/h) and gusts of up to 132mph.

It was downgraded from a super typhoon on Saturday – with its sustained winds falling below 150mph – as it passed through the Luzon strait separating the Philippines and Taiwan, probably sparing residents in both places from the most destructive winds near its eye.

In the Philippines, Usagi left at least two dead – a man aged 50 and woman aged 20 – and two others missing after a passenger boat capsized in rough waters off north-eastern Aurora province. In Taiwan, nine people were hurt by falling trees on Kinmen island off China's coast.

The typhoon landed near the city of Shanwei in the Chinese province of Guangdong, about 87 miles (140km) north-east of Hong Kong, and was moving west-north-west at 140 mph, the Hong Kong Observatory said. It was expected to skirt about 60 miles north of Hong Kong.

Ferry services between Hong Kong and Macau and outlying islands were suspended as the observatory raised the No 8 storm warning signal, the third highest on a five-point scale. It reported winds as strong as 42mph and warned that a storm surge and heavy rains could cause flooding in low-lying areas.

Police in Shanwei ordered more than 8,000 fishing boats to return to port and more than 1,200 residents were taken to temporary shelters, China's official Xinhua news agency reported.

The typhoon wreaked havoc on airport schedules in Hong Kong, nearby Macau and mainland China, upsetting travel plans for many passengers who were returning home at the end of the three-day mid-autumn festival long weekend.

Hong Kong international airport said 370 arriving and departing flights had been cancelled and another 64 delayed. Two of Hong Kong's biggest airlines, Cathay Pacific Airways and Dragonair, cancelled flights to and from the city's airport starting at 6pm on Sunday, with plans to resume operations Monday if conditions permitted.

Beijing-based Air China cancelled 148 flights to and from Hong Kong, Macau and five nearby mainland cities. China Southern Airlines, based in Guangzhou, cancelled all flights to and from Hong Kong and three mainland airports, Xinhua said.

Fujian province suspended shipping between mainland China and Taiwan, the news agency said.

Authorities in Guangdong initiated an emergency response plan for the Daya Bay nuclear power station north-east of Hong Kong as Usagi approached, ordering four of six reactors to operate at a reduced load, Xinhua said.

In Taiwan, more than 3,300 people were evacuated from flood-prone areas and mountainous regions. The storm also caused a landslide that buried a rail line on Taiwan's south-east coast, but rail services were restored by Sunday morning.

Another landslide late on Saturday in the south-eastern hot springs resort village of Chihpen sent mud and rocks crashing through the ground floor of a resort spa, forcing the evacuation of frightened guests. The Chihpen river breached its levees upriver, turning the village's main street into a rock-strewn stream, flooding homes and damaging vehicles.