The most powerful typhoon of 2013 battered the Philippines and Taiwan on Saturday, as it eyed landfall in Hong Kong.

Typhoon Usagi had maximum sustained winds of 222 kilometres per hour (139 miles per hour) and gusts exceeding 260kph (163mph) on Saturday morning, and was 550 kilometres (342 miles) south of Taipei, Taiwan's capital, according to the U.S. Navy's Joint Typhoon Warning Center.

Taiwan's Central Weather Bureau said Usagi was veering west, likely sparing southern Taiwan from the most destructive winds near its eye.

In the Philippines, Usagi triggered landslides and power outages in parts of the north of the country. No casualties have been reported.

China's National Meteorological Center announced a red alert, its highest level, as the storm maintained its track toward Hong Kong and the manufacturing heartland of the Pearl River Delta. The observatory warned that Usagi would impact coastal areas of Guangdong, Zhejiang and Fujian provinces.

The Hong Kong Observatory said that Usagi was 650 kilometres (406 miles) east-southeast of the city. It said the storm's maximum sustained winds would weaken to 165kph (103mph) on Sunday on approach to Hong Kong before making landfall overnight. The observatory was maintaining a No. 1 Standby Signal and warned that the storm poses a "severe threat" to the city.

In Taiwan, nearly 2,500 people were evacuated from flood-prone areas and remote mountainous regions as the government deployed military personnel into potential disaster zones. The storm system has dumped more than 200 millimetres (8 inches) of rain along the eastern and southern coasts over a 13-hour period, with officials warning that a total rainfall of 1,000 millimetres (39 inches) could drop before the storm leaves on Sunday.

Usagi has a massive diameter of 1,100km (680 miles), with its outer rain bands extending across Luzon and all of Taiwan across to the Chinese coast.

The Office of Civil Defense in Manila said landslides damaged houses and roads, and pockets of power outages were reported in at least five northern provinces, where several roads and bridges were impassable.

Airlines Cathay Pacific Airways and Dragonair both warned of delays and cancellations at Hong Kong International Airport from Sunday evening to Monday morning, and urged passengers to postpone nonessential travel on those two days.