Qantas has flagged flight disruptions between Hong Kong and Australia as the Asian financial hub prepares for one of its strongest super typhoons in years.
Hong Kong's airport is expected to remain open in some capacity, with the city's airport authority saying flights will be significantly reduced from Tuesday evening, with most flight operations affected on Wednesday.
Hong Kong's flag carrier Cathay Pacific Airways has signalled 500 of its flights are expected to be cancelled, while Qantas warned its flights in and out of Hong Kong could be suspended for 36 hours from Tuesday evening, adding the airline will contact customers who are affected.
Ragasa is expected to sweep south of Hong Kong and Macao, with all schools in the regions closed for the next two days.
Thousands of people have evacuated from northern Philippine villages as the super typhoon swept across the country, threatening to cause flooding and landslides on its way to south-eastern China.
Ragasa had sustained winds of 215km/h with gusts of up to 295km/h when it slammed into Panuitan island off Cagayan province on mid-afternoon Monday, Philippine forecasters said.
Tropical cyclones with sustained winds of 185km/h or higher are categorised in the Philippines as a super typhoon, a designation adopted years ago to underscore the urgency tied to such extreme weather.
Ragasa was heading west and was forecast to remain in the South China Sea at least into Wednesday, passing south of Taiwan and Hong Kong before making landfall on the Chinese mainland.
The Philippines' weather agency warned of coastal inundation, saying "there is a high risk of life-threatening storm surge with peak heights exceeding three metres within the next 24 hours over the low-lying or exposed coastal localities" in the northern provinces of Cagayan, Batanes, Ilocos Norte and Ilocos Sur.
Power was knocked out on Calayan Island and in the entire northern mountain province of Apayao, disaster-response officials said.
Philippine President Ferdinand Marcos Jr suspended government work and all classes on Monday in the capital and 29 provinces in the main northern Luzon region.
More than 8,200 people were evacuated to safety in Cagayan, while 1,220 others fled to emergency shelters in Apayao, a province prone to flash floods and landslides.
Taiwan's southern Taitung and Pingtung counties ordered closures in some coastal and mountainous areas, as well as on the outlying Orchid and Green islands.
Ragasa also forced the cancellation of afternoon flights to outlying islands and suspended various ferry services, the Central News Agency reported.
The typhoon is expected to bring torrential rains and heavy winds to China's mainland coastal areas, starting Tuesday.
