Typhoon Mangkhut hurtled towards Hong Kong on Sunday (Sep 16), lashing its coastline and sending skyscrapers swaying, after killing dozens in the Philippines and ripping a swathe of destruction through its agricultural heartland.

Typhoon Mangkhut hit Hong Kong on Sunday (Sep 16), leaving fallen trees and sign posts on the roads in Prince Edward, Hong Kong. (Photo: Phoebe Wong)

The massive storm, considered the world's biggest this year, has already left large expanses of the Philippines' Luzon island underwater as its fierce winds ripped trees from the ground and rains unleashed dozens of landslides.

In Hong Kong, weather authorities issued the maximum alert for the storm, which rocked the city with fierce gusts that have reportedly reached 232 kilometres per hour.

As the storm tore past south of Hong Kong, trees were snapped in half and roads blocked, while windows and walls in tower blocks and skyscrapers were smashed.

"We're just afraid the window will break in any minute. We keep receiving lots of video from WhatsApp (showing) flooding, flying rubbish bin. Some colleagues' homes have lost electricity already; we have readied torch and candle by our side," Ms Phoebe Wong, 47, a field sales supervisor at Procter & Gamble, told Channel NewsAsia.

Typhoon Mangkhut hit Hong Kong on Sunday (Sep 16), leaving fallen trees and sign posts on the roads in Prince Edward, Hong Kong. (Photo: Phoebe Wong)

According to AP, at Hong Kong's Heng Fa Chuen housing estate, large amounts of water were seen hitting the promenade among the waterfront. Authorities hoisted the highest No 10 tropical cyclone signal at 9.40am (0140 GMT), warning residents to be mindful of safety and to avoid waterfront areas.

Hong Kong residents in fishing villages such as Tai O were assisted by government officers to evacuate, to mitigate damage from flooding in low-lying areas, AP added.

Water levels in Hong Kong's famous Victoria Harbour and fishing villages could surge by up to four metres, authorities said earlier, and hundreds of residents have been evacuated to storm shelters as the observatory forecast severe flooding for low-lying areas.

Shop windows were taped up and the normally traffic-clogged streets were deserted as the storm drew nearer.

The government has warned people to stay indoors but some were strolling in the park or along the waterfront on Sunday morning.

"I went running this morning. I love fresh air and there's no one on the streets, no cars. On normal days we can't see this," said Hao Chen, 28, who lives in the neighbourhood of Tin Hau, on Hong Kong Island.

Some residents reported their buildings were swaying in the wind and parks were already strewn with broken branches by the early morning.

Resident Antony Kwok in the fishing village of Tai O said flood shields and ladders had been set up to protect those who live in the area's stilt houses as waters began to rise, in a post on Facebook Live.

Almost all flights in and out of Hong Kong have been cancelled.

Preparations were in high gear on China's southern coast, including in Yangjiang, which is not often hit by major typhoons and where the city's 2.4 million people were bracing themselves for a direct hit.

Further down the coast preparations were also underway in Zhanjiang, where some villagers feared for the worst.

"I couldn't sleep last night, I saw the typhoon on television and how intense it was," said 55-year-old Chan Yau Lok.

Nearly half a million people had been evacuated from seven cities in Guangdong province, according to AP.

The gambling enclave of Macau closed down casinos for the first time.​

Streets in parts of Macau were underwater as a storm surge sent water gushing from the harbour into the city.

The government and casinos are taking extra precautions after Macau was battered by Typhoon Hato last year, which left 12 dead.

Mangkhut is due to make landfall in Guangdong later Sunday.

The national meteorological centre said southern China "will face a severe test caused by wind and rain" and urged officials to prepare for possible disasters.

On Sunday morning, the typhoon packed sustained winds of 155 kph and gusts of up to 190 kph, AP reported.

The Hong Kong Observatory said although Mangkhut had weakened slightly, its extensive, intense rainbands were bringing heavy downfall and frequent squalls.

All high-speed and some normal rail services in Guangdong and Hainan provinces were also halted on Sunday, the China Railway Guangzhou Group Co said.

Super Typhoon Mangkhut. (Graphic: AFP/Gal Roma)

The typhoon has been gaining in strength over the South China Sea after tearing through the Philippines.

Mangkhut, the Thai name for Southeast Asia's mangosteen fruit, was expected to skirt 100km south of Hong Kong and veer west towards the coast of China's Guangdong province, and the gaming centre of Macau later in the day./.

VNF/CNA