BEIJING, August 8, 2008 (AFP) - Three foreign pro-Tibet activists staged a brief protest near Beijing's Olympic stadium Friday, one hour before the start of the opening ceremony for the Games, an activist group said.

The three, two Americans and one Argentine-American, displayed Tibetan national flags, but Chinese security tackled them 40 seconds after the protest began, Students for a Free Tibet said in a statement.

They were immediately and forcibly detained, the group said.

'These activists have delivered a message of solidarity with the Tibetan people, highlighting the grave situation in Tibet just moments before the Beijing Olympics began,' said Lhadon Tethong, Executive Director of Students for a Free Tibet.