The Canadian Consulate in Hong Kong has banned staff from travelling outside the city, including to mainland China.
The move comes days after a British Consulate worker was detained there.
The Chinese government’s announcement this week that Simon Cheng Man-kit has been detained in the city of Shenzhen has stoked tensions in Hong Kong, which has been gripped by months of anti-government protests.
The Canadian Consulate said in a statement on Friday: “At present, locally engaged staff will not undertake official business travel outside of Hong Kong.”
It did not say whether the travel restriction was directly related to the detention of Mr Cheng, who went missing two weeks ago after going on a business trip to the mainland city from Hong Kong’s high-speed cross-border rail terminal.
China said this week that Mr Cheng had been placed in administrative detention for 15 days for violating public order regulations. It did not elaborate.
Mr Cheng has been working for the British Consulate since December 2017 as an international trade and investment officer for the Scottish Government. He and other local staff at consulates and embassies support diplomats but do not have diplomatic passports themselves.
The Global Times, a Communist Party-owned nationalistic tabloid, reported on Thursday that Mr Chen was detained for “soliciting prostitutes”.
Police in Shenzhen would not confirm the report.
China often uses public order charges against political targets and has sometimes used the charge of soliciting prostitution.
Ou Shaokun, an anti-corruption activist, alleged in 2015 that he was framed by authorities in southern Hunan province who said they found him in a hotel room with a prostitute.
The UK’s Foreign and Commonwealth Office said in a statement that they are still urgently seeking further information about Mr Cheng’s case.
The Foreign Office said: “Neither we nor Simon’s family have been able to speak to him since detention.
“That is our priority and we continue to raise Simon’s case repeatedly in China, Hong Kong and London and have sought to make contact with Simon himself.”
The Canadian government also updated its travel advice for China on Thursday to warn of stepped-up border checks on phones.
“Increased screening of travellers’ digital devices has been reported at border crossings between mainland China and Hong Kong,” the advisory said.
There have been increasing reports that Chinese immigration officers are inspecting phones for photos related to the Hong Kong protests.
The head of the cabin crew union for Hong Kong airline Cathay Dragon also said she had been fired in retaliation for supporting the movement, adding to the chill in the semi-autonomous Chinese territory where protesters have been rallying for more than two months.
Meanwhile, accountants in Hong Kong have marched in support of the pro-democracy movement.
Demonstrators are planning to form human chains stretching for 25 miles on Friday night to show their resolve.
They said this “Hong Kong Way” demonstration was inspired by the “Baltic Way” protests, when people in the Baltic states joined hands 30 years ago in protest against Soviet control.
A few thousand accountants gathered in a city square around noon and marched to government headquarters, becoming the latest profession to publicly back the movement following rallies by lawyers, teachers and medical workers.
One participant, Sarah Wong, said accountants are usually quiet because they are focused on getting the numbers right, but they cannot remain silent any more.
Kenneth Leung, an MP who represents the accounting industry, said that the now-suspended extradition bill that sparked the protests would have affected accountants, because many of them have clients in mainland China and often travel there.
The legislation would have allowed suspects to be extradited to the mainland to face trial.
“The profession as a whole needs to come out to express their concerns and grievances,” he said.
Rebecca Sy, the airline union head, told a news conference that Cathay Dragon dismissed her without giving a reason, but that the firing came after she was pulled from a flight at short notice and asked by an airline representative to confirm that a screenshot from Facebook was from her account.
Cathay Dragon is owned by Hong Kong’s main carrier, Cathay Pacific, which has come under pressure from Chinese authorities for employing people who support the protests.
Ms Sy said: “It’s not just about the termination of the job, it’s also the whole issue, it’s terrifying. All my colleagues are all terrified.
“I feel so sorry for them because I’m no longer in that position to protect them. I used to be the one to stand behind them, to back up all of my colleagues.”
The Hong Kong Confederation of Trade Unions called her firing a “blatant suppression and retaliation on her participation in the anti-extradition bill movement and her actions to mobilise her colleagues to participate as a trade union leader”.