President Ferdinand Marcos Jr ordered the Philippines disaster response agency to go on full alert and mobilise all government agencies as Super Typhoon Ragasa threatened the north of the country and set off storm alerts across East and Southeast Asia.
Packing winds of 215 kph (134 mph) and gusts of up to 295 kph (160 mph), Ragasa made landfall in Calayan Island in Cagayan province, raising the risk of storm surges exceeding three metres (nine feet), the state weather agency said.
The Babuyan islands remained under a high-level storm warning signal, with residents advised to stay away from coastal areas and riverbanks.
Video clips shared by disaster agencies showed the northern Cagayan province being pummelled by fierce winds and heavy rain, triggering strong waves and sending trees swaying violently.
The government suspended work and classes across Metro Manila and large parts of Luzon as outer rainbands began lashing the region, prompting warnings of power outages, landslides, floods, and dangerous seas.
Airlines have cancelled two dozen domestic flights, mostly serving Luzon's main hubs, while ports have suspended ferry services.
Although Ragasa will not directly hit Taiwan, its outer bands are expected to bring heavy rain to the island's sparsely populated east coast. Taiwan has issued land and sea warnings, cancelled 146 domestic flights, and evacuated more than 900 people from mountainous southern and eastern areas.
Vietnam's defence ministry has ordered its forces to monitor the storm and prepare for a possible landfall later this week.
Chinese authorities have activated flood control measures in several southern provinces, warning of heavy rain beginning Tuesday night.
Hong Kong said its airport will remain open, but operations will be scaled down. Yeung Tat-wing, director of service delivery at the Hong Kong Airport Authority, said flight operations would be significantly reduced after 6 p.m. (1000 GMT) on Tuesday, and most flights will be affected on Wednesday. Cathay Pacific said it will cancel about 500 flights.
Macau and Zhuhai are also bracing for impact, with school closures and evacuation plans under way.
In Hong Kong, residents started stockpiling daily necessities on Monday morning. Long queues formed at supermarkets where products like milk had already sold out, while vegetables were being sold for more than triple their normal price at fresh markets, according to Reuters witnesses.