Chinese police detained a well-known Marxist at a top university on Wednesday, a witness said, on the sensitive anniversary of the 125th birthday of the founder of modern China, Mao Zedong, whose legacy remains deeply contested.

Qiu Zhanxuan, head of the Peking University Marxist Society, was grabbed and forced into a black car outside the east gate of Peking University by a group of heavy-set men who identified themselves as police, a student said.

"I saw a black car parked by the gate and seven or eight men in plainclothes lifting him by his arms and legs and forcing him into the car," the student said, declining to be named due to the sensitivity of the situation.