British Foreign Secretary Philip Hammond warned over threats to Hong Kong's autonomy Friday as he visited the city where fears are growing that Beijing's grip is tightening.
It was the first visit by a British foreign secretary for five years and comes in the wake of a high-profile case in which a group of Hong Kong booksellers went missing, only to surface in China.
One of the booksellers was British citizen Lee Bo, whose case caused the greatest outcry as he was the only one to disappear from Hong Kong, prompting accusations that Chinese law enforcement agents were operating in the semi-autonomous city, illegal under its constitution.
"We believe that he was removed under duress to the mainland... now our principal concern is that he is returned to Hong Kong free of any duress and able to carry on his life here without any constraints or impositions on him," Hammond told reporters at the city's British consulate on Friday.
Hammond said he will raise the issue with China's foreign minister Wang Yi in a Saturday meeting in Beijing, adding that people were nervous over the incident.
"There are people in the business community who are unnerved by this incident and we need everybody to make very clear this is not going to happen again," he said.
In a meeting with Hong Kong's leader Leung Chun-ying, the British Foreign and Commonwealth Office (FCO) said that Hammond would restate "support for Hong Kong's high degree of autonomy, rights and freedoms", as well as commitment to the Sino-British joint declaration which protects Hong Kong's liberties.
The city has been semi-autonomous since it was handed back to China by Britain in 1997 under an agreement that protects its freedoms for 50 years. However, there are concerns those freedoms are disappearing.
The five booksellers worked for a Hong Kong publishing house famous for salacious titles about high-ranking Chinese politicians. They went missing at the end of last year.
Four are under criminal investigation in the mainland -- the fifth, UK citizen Lee Bo, says he is "assisting" with the investigations and has come back to visit Hong Kong recently, insisting he is a free man.
Britain has voiced anger over Lee, saying it believed he was "involuntarily removed to the mainland" from Hong Kong in what it called a "serious breach" of the handover agreement.
China criticised the UK for interfering in its affairs.
The other four men disappeared from Thailand and mainland China.
The FCO added that Hammond would also "underline the importance of One Country, Two Systems and of restarting progress on political reform" in his meeting with Leung later Friday.
The political reform process has stalled since mass pro-democracy protests in 2014 failed to win concessions from the Hong Kong authorities and Beijing.
The rallies were calling for fully free leadership elections, after the government introduced a reform package that activists derided as fake democracy because it allowed Beijing to vet candidates.
The package was eventually voted down in the legislature and the reform debate is now on ice.
Hammond's visit is the first stop on an east Asia tour, ahead of the G7 foreign ministers' meeting in Japan starting on April 10.
He will also meet members of Scotland's Rugby Sevens team as the Hong Kong Sevens tournament kicks off on Friday, as well as Hong Kong and British businesses "to discuss new ways of connecting the UK, Hong Kong and China markets", the FCO said.