A landmark stock trading link program allowing Hong Kong and Shanghai investors to buy and sell shares on each other's bourse is officially launched on Monday, marking the start of one of China's most significant moves to further open its capital markets.

Hong Kong's [Company Incorporation USA]Chief Executive Leung Chun-ying welcomed the launch of the pilot program to provide mutual trading access between the Shanghai and Hong Kong stock markets.

Leung said the program will increase the competitiveness of both stock markets and enhance Hong Kong's status as a major offshore renminbi trading hub.

"It is a breakthrough in the opening up of China's financial markets and an important milestone in the development of Hong Kong as a unique gateway between the mainland and international investors," Chairman of the Hong Kong Exchanges and Clearing Limited Chow Chung-kong said at the launching ceremony.

A-share buying under the program reached its daily maximum amount of 13 billion yuan ($2.1 billion) by 1:57 pm, as international investors piled into mainland stock market on the first day of the trading link.

Mainland investors invested about 1.4 billion yuan in Hong Kong shares out of their 10.5 billion yuan quota.

According to the program, investors can only place sell orders once the daily quota is maximized.

On the Southbound link, institutional investors and individuals with over 500,000 yuan ($81,421) in their brokerage accounts may trade Hong Kong shares through a broker on the Shanghai stock market; while heading Northbound, Hong Kong investors and international investors with Hong Kong brokerage accounts may trade shares listed on the Shanghai stock market.

There are 568 eligible stocks for Northbound trading, namely constituent stocks of the Shanghai Stock Exchange 180 Index and SSE 380 Index as well as shares that are dual listed in the two bourses (A+H shares). For Southbound, investors will be able to trade 268 eligible stocks, namely constituent stocks of the Hang Seng Composite LargeCap Index and Hang Seng Composite MidCap Index as well as shares that are dual listed in the two bourses (A+H shares).

Chinese shares opened higher and slid to a modest rise on Monday as the Shanghai-Hong Kong stock connect pilot program debuted.

The benchmark Shanghai Composite Index advanced to 2,495.80 points, up 16.98 points, or 0.68 percent in the morning trading session.

Since the program was officially approved in April, it took more than seven months for it to be launched. [Hong Kong Company Registration Guide]The SCI has also risen over 18 percent since April.

The Shenzhen Component Index on Monday rose to 8,361.21, up 34.31 points, or 0.41 percent.

Hong Kong stocks slid 0.5 percent to 23,974 in the morning trading session, in part dragged by the decrease of the blue-chip Hong Kong Exchanges and Clearing Limited.