Nathan Law, who lives in exile in the UK, said he arrived in Singapore on Saturday to attend a “closed-door, invitation-only” conference but was detained at the border for four hours.

“I was not asked questions and they did not give a reason for the denial,” the 32-year-old told the BBC. In a separate statement, Law said he believed the refusal was for “political” reasons. “I am unsure whether external forces, such as the PRC (People’s Republic of China), are involved, directly or indirectly,” he added. The BBC has reached out to Singapore’s immigration and home affairs ministries. The organisers of the event declined to comment.

Law said he had applied for a visa allowing “one-time entry for a few days,” which was approved three weeks before his departure. He holds a UK Refugee Travel Document. According to Law, he was placed on a return flight to San Francisco, where his journey had begun.

The activist is one of the most prominent figures in Hong Kong’s pro-democracy movement. He fled the city in 2020 after Beijing imposed a sweeping national security law criminalising secession, subversion and terrorism, with penalties of up to life imprisonment. In 2021, he was granted asylum in the UK.

Law is wanted by the Hong Kong government, which accuses him of endangering national security. Singapore has an extradition treaty with Hong Kong. Authorities in the territory have also offered rewards of HK$1m ($128,000; £95,000) for information leading to the arrest of Law and other activists.

This is not the first time Singapore has acted against Hong Kong pro-democracy figures. In 2019, the city-state fined a Singaporean activist for organising an online forum that had featured prominent activist Joshua Wong via teleconference. (BBC)