Prominent intellectuals Yu Jie and Liu Xiaobo were taken away by mainland police yesterday in what is seen as the latest crackdown by authorities on dissent. Five Beijing Public Security Bureau officers took Mr Yu away for interrogation at about 6.30pm, his wife, Liu Min, said. Ms Liu said police later told her that Mr Yu's detention was due to his participation in 'activities that jeopardise national security'. Mr Yu, 31, has become an influential writer on the internet after his printed works were banned. Mr Liu, another banned writer who is prolific on the internet, is understood to have been taken away, along with his wife, Liu Xia. Mr Liu, 48, had been jailed for leading a hunger strike among intellectuals in 1989 and for writing a petition in 1996 calling for Tibet to be given self-determination. Friends close to both writers link the detentions to their involvement in the international writers' group PEN, which promotes freedom of expression, and authorities' efforts to tighten control over cyberspace.