HONG KONG: Torrential rain deluged Hong Kong on Friday leading to widespread flooding across the densely packed city, submerging streets, shopping malls and metro stations, as authorities shut schools and asked workers to stay at home.

The Chinese special administrative region saw the highest hourly rainfall since records began 140 years ago. Cascades of water tumbled down the city's mountainous terrain as authorities issued landslide risk warnings.

Streets turned into torrents, videos circulating on social media showed, while one clip showed metro workers wading waist deep in a station as they tried to stem the water flow gushing down from road level.

The city's cross harbour tunnel, one of main arteries connecting Hong Kong island to Kowloon, was also inundated with water, while photos showed a waterlogged shopping centre in the Chai Wan district.

Hong Kong Observatory reported rainfall of 158.1 millimetres (6.2 inches) between 11 p.m. HKT on Thursday and midnight on Friday (1500 to 1600 GMT on Thursday).

The weather bureau issued the highest "black" rainstorm warning and said more than 200 mm of rainfall was recorded on Hong Kong's main island, Kowloon and the northeastern part of the city's New Territories since Thursday night.

The trough of low pressure associated with the remnant of Typhoon Haikui has brought torrential rain to the coast of China's Guangdong since Thursday, the weather bureau said.

Extreme conditions are expected to last until at least noon on Friday.

Hong Kong's stock exchange will not open on Friday morning and will remain shut for the afternoon session if the "black" rainstorm warning remains in place by noon, the exchange said.

City leader John Lee said he was very concerned about the severe flooding in most parts of the territory and had instructed all departments to respond with "all-out efforts".

Some passenger and cargo clearance points at two border control points between Hong Kong and neighbouring city Shenzhen were suspended due to flooding, the government said.

In the city's Wong Tai Sin district, vehicles were submerged in water as they tried to drive down a main road.

Hong Kong's MTR Corp 0066.HK which operates the city's rail network said at least one line was shut while others were operating at delayed intervals.

All schools have been suspended on Friday due to "extreme conditions caused by extensive flooding and serious traffic disruption," the government said.

It appealed to employers to observe work arrangements normally used for the strong wind signal 8, which brings the city to an effective standstill with offices and stores shut.Macau ferry operators in Hong Kong said several ferry trips would be suspended to the gambling hub due to widespread flooding in the financial centre.

Macau's weather bureau issued the lowest "yellow" rainstorm warning on Friday which allows schools and businesses, including the casinos to open as normal.