A plan for mainland border staff to be stationed on Hong Kong soil as part of a new rail link to China sparked a backlash Tuesday as concern grows about Beijing's reach into the city.

It is illegal for mainland law enforcers to operate in semi-autonomous Hong Kong under the city's mini-constitution, the Basic Law.

But there are already concerns that Chinese operatives are working undercover after the alleged abductions of a city bookseller and a reclusive Chinese businessman.

The rail link plan comes at a time when fears are worsening that Hong Kong's freedoms are under threat from an ever more assertive Beijing.

The high-speed connection out of the harbourfront West Kowloon station is set to open in 2018, linking to the southern Chinese city of Guangzhou 80 miles (130 km) away and then onto China's national rail network.

A proposal approved by the Hong Kong government's top advisory body Tuesday would see parts of the Hong Kong terminus fall under Chinese jurisdiction.

There are already numerous transport connections between Hong Kong and the mainland, but Chinese immigration checks are done on the other side of the border.

City leader Carrie Lam insisted the new checkpoint arrangement was not a breach of the Basic Law and was designed to cut travel time.

"The crux of the matter is really to find a means that is legal to support this convenience for the people of Hong Kong," Lam told reporters.

- 'State property' -

The government's pro-Beijing camp has said Hong Kong is simply "leasing" the portion of land at the terminus to China.

But veteran lawyer and democracy advocate Martin Lee, who helped draft the Basic Law in the 1980s, said creating an exception within Hong Kong where mainland Chinese laws are enforced would set a "dangerous precedent".

It would put at risk the semi-autonomous "one country, two systems" set-up guaranteed when Britain handed Hong Kong back to China in 1997, Lee told AFP.

The government wanted to force through the plan to make Hong Kong people "feel closer to Beijing, the sovereign power", added opposition legislator Claudia Mo.

Faced with a barrage of reporters' questions Tuesday afternoon, justice secretary Rimsky Yuen pointed out that, under the Basic Law, Hong Kong's land and natural resources were "state property".

He said the mainland area of the terminus would be regarded as outside the territorial boundary of Hong Kong and that Chinese rules would apply.

Yuen was unsure whether websites like Facebook, banned on the mainland, would be accessible in China's portions of the station.

Parts of the arrival level and departure level of the terminus will be under Chinese jurisdiction, as will the platform level and train cabins.

Mainland staff stationed at the terminus will include customs, immigration and health officials, as well as police.

The plan now needs approval from the city's legislature, which is weighted towards the pro-China camp.

The rail link is one of a number of cross-border infrastructure projects which have stoked fears Hong Kong is being swallowed up by the mainland.

Passengers from Hong Kong could reach Beijing in under 10 hours on the new line, but controversies have plagued the project, with snowballing costs now at HK$84.42 billion ($10 billion).

Source: AFP