Photo/Illutration In this Nov. 1, 2018 file photo, Kenneth Roth, Human Rights Watch's executive director, speaks during a news conference in Seoul. (AP Photo)

HONG KONG--Hong Kong authorities barred the head of Human Rights Watch from entering the Chinese territory Sunday, the advocacy group said.

Kenneth Roth, Human Rights Watch's executive director, had planned to launch the organization's annual world report in Hong Kong this week. The report's focus is China's efforts to “deliberately undermine the international human rights system," Roth said in video posted to his Twitter.

The move to bar Roth follows China's pledge last month to sanction organizations that it said “performed badly" in relation to anti-government protests that have roiled Hong Kong for more than seven months. Human Rights Watch, the National Endowment for Democracy and Freedom House were among the groups cited for sanctions.

Roth, a U.S. citizen, said on Twitter that immigration authorities at the airport told him he could not enter Hong Kong. When he asked why, they told him repeatedly that it was for “immigration reasons," without elaborating.

Roth said he has visited Hong Kong numerous times and this is the first time he has been denied entry.

Mass demonstrations — underpinned by a distrust of China's ruling Communist Party — began in Hong Kong in June, with protesters rallying against an extradition bill that was later withdrawn. The movement has since expanded to include demands for electoral reform and an independent inquiry into alleged police brutality.

A former British colony, Hong Kong was returned to China in 1997. Under the framework of “one country, two systems," the territory was promised greater democratic rights than are afforded to the mainland. But protesters say their liberties have been steadily eroding under Chinese President Xi Jinping.

“My denial of entry pales in comparison to the harassment that Chinese activists routinely endure," Roth said in a Human Rights Watch statement.

“China's efforts to interfere with the work of international groups like Human Rights Watch is a form of global censorship that government should resist before it's too late," he said.