VANCOUVER, British Columbia -- Police dragged a protester off the stage and officers tackled a woman with a bandanna over her face Monday during a ceremony marking the three-year countdown to the Winter Olympics in Vancouver.

Despite heavy security at the downtown event with dozens of officers in yellow jackets, including some on horseback and in riot gear, one protester managed to leap onto the stage and push the master of ceremonies out of the way. The protester shouted obscenities into the microphone before being dragged off by officers.

Police said protesters hurled eggs, paint-filled balloons and paper mache balls filled with rocks.

"I'm dismayed by the fact that these people want to cross the line and start throwing things at police officers. That's the part that's upsetting to everybody here," said Const. Howard Chow, a spokesman for the department.

The Vancouver Organizing Committee for the 2010 Games held the ceremony Monday to unveil a huge digital clock on the grounds of the downtown art gallery to count down the time left before the opening ceremonies on Feb. 12, 2010. The other side of the clock displays the time left before the Paralympics, which begin a month later.

The clock, a permanent installment, was given to the city by Omega, the Games' official timekeeper.

Hundreds of people crowded into the square to watch the ceremonies, but in a corner of the site, activists unveiled their own so-called doomsday clock. The cardboard creation marks significant events in the decline of government support for social housing and concludes that by 2010, 6,000 people will be homeless in the city.