Authorities in the eastern Chinese province of Jiangsu have detained a rights activist, who was then fired from his job while in police custody, after he used Twitter to support human rights causes, RFA has learned. Shi Jing was prevented from boarding a flight to Japan by police in Jiangsu's provincial capital Nanjing at the beginning of this month, and held in detention by them until Thursday, he told RFA following his release. Shi had been unaware that he was unemployed until his father, fellow rights campaigner Shi Tingfu, went to speak to his employer while he was in police custody. "I asked my father to go to my workplace to help me arrange leave, and they told him that I had been fired from the company because I was a person in custody," Shi said. "This is a state-owned enterprise, so I guess that's why." "They probably came under pressure[to fire me] after finding out what had happened to me," he said. Shi, who had worked as a driver for the company for several years, said he didn't know of any issues with his performance. While in detention, police had confronted him with posts he made to Twitter, which is blocked by the ruling Chinese Communist Party's censors. The offending tweets included the case of human rights lawyer Wang Quanzhang, held for more than three years in incommunicado, pretrial detention. "[There was also] one about a woman who splashed ink[on a portrait of Chinese President Xi Jinping]," he said. "They also went and deleted my Twitter account." "Now my passport has been revoked, along with my entry permit to Hong Kong and Macau, and I can't leave the country," Shi said. "They said they'd be watching my behavior, and warned me not to post anything that was a sensitive topic relating to the government." Shi's father Shi Tingfu said he supports his son's activism. "I think what he does is meaningful, I don't object, and support him," he told RFA. Travel ban thwarts Taiwan trip In September, police had warned Shi Jing that he was under a travel ban, after learning that he planned to visit the democratic island of Taiwan, to observe elections there this month. Shi Jing was also warned by police not to "become a tool of hostile foreign forces," the Civil Rights and Livelihood Watch website reported at the time. Shi Tingfu was handed a suspended jail term last year after he staged a public memorial ceremony for the victims of the 1989 Tiananmen massacre, and also remains under close police surveillance. "I have been unemployed for a while now," he said. "I wanted to sell things on a street stall but they wouldn't let me do that, and I have no work, so[Shi Jing's firing] will make life much harder." "My son used to complain about it, but now he's grown, he understands better ... he has been supporting Wang Quanzhang's case for so many years now," he said. Shi Tingfu was taken away by police in June 2017 after he defied a nationwide ban on public events marking the anniversary of the 1989 student movement and the subsequent bloody crackdown by the People's Liberation Army (PLA). He was charged with "picking quarrels and stirring up trouble" for wearing a T-shirt bearing the slogan "Never Forget June 4," Shi made a public speech to passers-by outside the Nanjing Massacre Memorial Hall. In his speech, Shi called on bystanders to remember that the anniversary was "a sad day for many mothers," and asked them to post footage and photos of his speech online to make more people aware of the 28th anniversary of the crackdown. Public memorials and discussions of the events of June 1989 are banned in China, with activists who seek to commemorate the bloodshed often detained and veteran dissidents placed under police surveillance or detention during each anniversary. An unknown number of people were killed by advancing PLA troops and tanks in Beijing on the night of June 3-4, 1989, following orders to clear the square by force from then-supreme leader Deng Xiaoping.