China's southern regions faced more heavy rainfall on Monday as a devastating typhoon swept west, a day after wreaking havoc in Hong Kong and Macau and killing potentially more than 50 people in the Philippines.

China Meteorological Administration said early on Monday rainfall from the typhoon, dubbed the "King of Storms", was expected to reach 100-160 millimeters (4-6 inches).

It said Mangkhut was located in Hengxian in Guangxi at 6 a.m. HK/SIN (2200 GMT Sunday) and had weakened to a "tropical storm." The storm was also due to hit the regions of Guizhou, Chongqing and Yunnan on Monday.

Packing winds of more than 200 kph (125 mph) at its peak, tropical cyclone Mangkhut is considered the strongest to hit the region this year.

Its strength outstripped that of Hurricane Florence, which achieved maximum sustained winds of 150 kph (90 mph) when it roared into North Carolina in the United States on Friday.

The eye of Mangkhut, the Thai name for Southeast Asia's mangosteen fruit, skirted 100 kms (62 miles) south of Hong Kong but the former British colony was still caught in the typhoon's swirling bands of rain and gale-force winds.

The financial hub of Hong Kong began clearing up on Monday after being battered by one of the strongest typhoons in recent years, with financial markets and offices operating as normal.

Super typhoon Mangkhut, with hurricane-force winds well over 200 kilometers per hour (124 miles/h), had barreled past the northern tip of the Philippines, killing at least 50 people. It then skirted south of Hong Kong and the neighboring gambling hub of Macau, before making landfall in China.

Parts of Hong Kong and Macau were severely flooded, though there were no immediate reports of any fatalities. Two people were reported killed in Guangdong, China's most populous province and home to over 100 million residents, state media reported.

The China Meteorological Administration said the typhoon, dubbed "King of Storms", swept west to Guangxi province at 6 a.m. (2200 GMT on Sunday) and weakened to a "tropical storm". It forecast the storm to hit the regions of Guizhou, Chongqing and Yunnan on Monday.

The meteorological administration said Mangkhut was one of the 10 biggest storms to hit southeast China since 1949 - when records began - with wind speeds at around 162 km/h.

Across Hong Kong, authorities strived to clear roads of debris, including toppled trees and bamboo scaffolding. Some buildings, including the One Harbourfront office tower, had many windows smashed after a day in which some of the city's skyscrapers had swayed with the ferocious gusts.

"Yesterday's storm was very strong. Even for a person of my weight, I was about to be blown down by the wind which made me very scared," said a 70-year-old resident surnamed Fung.

"It was very serious this time."

Stock and financial markets opened as normal on Monday in Hong Kong and the southern Chinese city of Shenzhen.

Some transport services remained suspended, though flights in the region were slowly resuming after a shutdown on Sunday, stranding many thousands of passengers.

In Macau, badly hit by a super typhoon last year, authorities were much more prepared this time, ordering casinos to close late on Saturday night as the storm approached.

Casinos were operational again early on Monday though authorities were still struggling to restore power to some of the 20,000 households that suffered power cuts.

Macau gambling stocks were down in early Monday trade.