Authorities in Vietnam briefly detained a prominent blogger shortly after his return to the capital Hanoi from Singapore, where he had attended a workshop on the use of a new mobile tool to promote citizen journalism, his daughter said Monday. Dung Mai was arrested Monday shortly after deplaning at the Noi Bai International Airport at around 6:00 p.m., his daughter Thao Teresa told RFA's Vietnamese Service. "My father sent me only one text, saying 'security officers in Noi Bai have arrested me'," Thao said from the airport, where she was waiting to receive Mai along with two of her friends. "We tried to speak with different[security] departments, but they have avoided telling us who was responsible[for his arrest]. I still don't know where my father is." Thao said she had traveled to the airport along with her friends Bui Tien Hung and Nguyen Van De, and that authorities had "sent two thugs to beat[them]." Around four hours after her father's plane landed in Hanoi, Thao was told that authorities had escorted him home, she said, adding that his phone had been turned off at the time of his detention. Thao's friend Hung told RFA that she displayed a sign which read that her father had been taken into police custody after receiving his text message, prompting authorities to confront them in the airport's main terminal. "Thao raised banners protesting the arrest and they sent thugs to take the banners away," he said. "I wasn't holding a banner, but a security officer ordered me to come to him. Then, two other people beat me right there in the main terminal of the airport with hundreds of people looking on." Hung did not elaborate on his condition after the assault. Land activist An active blogger, Mai has worked to assist victims of land disputes in Hanoi by providing them with food and other supplies. During the May 15-17 workshop in Singapore, Mai and 19 other netizens from Vietnam received training from RFA, the Saigon Broadcasting Television Network and Viet Tan-a U.S.-based pro-democracy organization banned by the Vietnamese government-on how to use a recently launched Vietnamese version of the StoryMaker mobile application. The open source app, which is available for Android mobile devices, allows users to produce and publish news in a safe and secure manner. In a statement issued at the end of the three-day launch and training event, Mai called StoryMaker "a powerful platform to spread the truth, to report on the challenges of Vietnamese victims of corruption and to provide a picture of today's Vietnam." The program concluded with a roundtable between attendees and international human rights nongovernmental organizations who discussed the challenges of Vietnam's media environment and ideas for protecting free expression. Last month, independent U.S. monitor group The Committee to Protect Journalists (CPJ) ranked Vietnam as the world's sixth most censored country in its annual list based on analysis of media suppression tactics such as imprisonment or harassment of journalists, repressive laws and restrictions on the Internet. The report said independent bloggers who report on sensitive issues in one-party communist Vietnam-which it called one of the world's worst jailers of journalists-have faced persecution through street-level attacks, arbitrary arrests, surveillance, and harsh prison sentences for anti-state charges.