Chinese e-commerce giant Alibaba has filed confidentially for a Hong Kong listing that will take place as soon as the third quarter of this year, a person with direct knowledge of the matter told Reuters. 

The listing could raise as much as $20 billion, sources said last month, smaller than its record $25 billion float in New York five years ago. 

At that time, founder Jack Ma expressed a desire to list in Hong Kong but the tech firm's management structure clashed with bourse rules. 

The stock exchange there has since changed its listing rules, mainly to attract China's tech startups. 

The latest deal would be the biggest follow-on share sale globally in seven years and give Alibaba ample funds for technology investment - a priority for China as economic growth flags and a trade spat with the US intensifies. 

The filing comes amid growing political unrest in Hong Kong this week that raised concerns over the potential impact on the city's financial market and businesses. 

Thousands of protesters have taken to the streets in the southern Chinese territory this week over a planned extradition agreement with mainland China. 

Logistics real estate developer ESR Cayman today pulled what would have been the largest Hong Kong listing so far this year due to weak demand, two people with direct knowledge of the matter said.

One person with direct knowledge of the matter said earlier the deal was more likely to be $10 billion to $15 billion. 

At $20 billion, the Alibaba deal would be the sixth-biggest follow-on share sale ever, Refinitiv data showed. 

Since its US listing, Alibaba has nearly doubled in size to become the largest-listed Chinese company with a market value of more than $400 billion. 

Listing in Hong Kong would give mainland Chinese investors their first direct access to one of the country's biggest success stories, via the stock connect trading link between Hong Kong, Shanghai and Shenzhen.