The international head of Human Rights Watch said he was denied entry to Hong Kong on Sunday, ahead of the launch of a report critical of the Chinese government.
Kenneth Roth, the group's executive director, said he was barred from entering the Chinese territory upon landing at the city's international airport on Sunday, with no reason given by immigration authorities.
"I had hoped to spotlight Beijing's deepening assault on international efforts to uphold human rights," Roth said in a statement on the group's website.
"The refusal to let me enter Hong Kong vividly illustrates the problem," he said.
The Hong Kong Immigration Department declined to comment on individual cases. In a short statement to CNN, it said the department considers "all relevant factors and circumstances of the case before deciding whether the entry should be allowed or not."
Hong Kong is in the midst of a months-long anti-government protest movement that calls for greater democracy and police accountability.
Mass demonstrations have at times turned violent as police fired tear gas and forcibly arrested protesters they accused of rioting and vandalism. Demonstrators have accused the police of using excessive force.
Roth, a US citizen who had freely entered Hong Kong before, said he had hoped to release Human Rights Watch's World Report 2020 at the city's Foreign Correspondents' Club on Wednesday.
The report, which reviews human rights practices in nearly 100 countries, is led by Roth's introductory essay that warns the Chinese government is carrying out an intensive attack on the global system for enforcing human rights.
Following the alleged denial of entry, Roth boarded a plane back to New York, where he will launch the report at the United Nations on Tuesday.
"I suppose I should be grateful to Hong Kong immigration authorities for this shoot-yourself-in-the-foot publicity for (Human Rights Watch's) World Report release," he said in a post on his Twitter account.
The semi-autonomous city has denied entry to a string of activists, foreign journalists and a US academic in recent years, drawing criticism at home and abroad for what some fear is an increasingly authoritarian approach in dealing with voices of dissent.
"This disappointing action is yet another sign that Beijing is tightening its oppressive grip on Hong Kong and further restricting the limited freedom Hong Kong people enjoy under 'one country, two systems,'" Roth said, referring to the arrangement under which the former British colony was returned to Beijing's rule.
Beijing has repeatedly denied interference and accused "foreign forces," including the US and the UK, as "black hands" behind the social unrest in Hong Kong.
Based in New York, Human Rights Watch was one of several US-based non-government organizations which the Chinese Ministry of Foreign Affairs had threatened to impose "sanctions" against in December.
They include the National Endowment for Democracy, the National Democractic Institute for International Affairs, the International Republican Institute and Freedom House.
The groups, which had been monitoring and reporting on the protests in Hong Kong, was accused by Beijing of supporting "anti-China" people. It said they were instigating protesters "engaging in extreme crimes" in pursuit of Hong Kong's separation from China.
HRW's criticism of China goes far beyond the Hong Kong protests. The group said fundamental rights and freedoms are "increasingly at jeopardy as Beijing seeks to broaden its repression globally."
