A Tibetan activist who burst into the Chinese embassy in Vienna and tore down its flag has claimed that he was then punched and beaten with a truncheon by security guards, a news report said.

On Thursday, Tibetan protester Tso Tashi Taoh stormed the embassy in front of a crowd of 200 demonstrators and tore down the Chinese flag before waving a Tibetan one in its place. He was held in the building for 45 minutes.

After his release, he said, he was punched in the face and beaten with a stick by Chinese security agents before his release, according to the report to appear Saturday in the Austrian newspaper Wiener Zeitung.

Embassy press attache Liu Chang described claims of a beating as "pure lies" but confirmed that the activist had been tied up during his brief detention.

Thursday's demonstration was called to protest China's crackdown in Tibet, where since last week there have been clashes between Chinese security forces and separatist Tibetan crowds seeking an end to rule from Beijing.