Nathan Law, a former Hong Kong lawmaker and pro-democracy activist, said he was denied entry into Singapore after arriving in the city on Saturday for a conference.

Law, who was a student leader during Hong Kong’s 2014 Umbrella Movement and later granted political asylum in the U.K., said Monday he’d been given a valid Singapore visa three weeks prior to his trip.

He was detained at immigration for four hours and then informed his entry was denied without being given a reason, he added. After that, he was deported back to San Francisco.

"It might have been under Chinese pressure, or Singapore’s internal political consideration that led to the U-turn,” he said. "I’m unsure of the situation.”

Singapore and Hong Kong authorities didn’t immediately respond to requests for comment, nor did China’s Foreign Ministry. Law’s entry denial was first reported by the Financial Times.

Law fled to London in 2020 after China imposed a national security law on Hong Kong, which brought unprecedented restrictions to a city accustomed to regular protests and a free media.

He faces arrest under the legislation if he returns to Hong Kong. Traveling to Singapore also carries some risk as the country maintains an extradition agreement with Hong Kong. Nations like Germany and Australia have suspended their treaties with Hong Kong since the security law was introduced.

Hong Kong has a 1 million Hong Kong dollar ($128,526) bounty each on Law and other activists who fled abroad to evade national security charges.