At least one gunman entered the Canadian Parliament buildings on Wednesday and many shots were fired just outside the room where Prime Minister Stephen Harper was addressing a meeting of legislators.

Harper was safely removed from the building but Parliament was locked down. Eyewitnesses said at least 30 shots were fired in dramatic scenes in the heart of the Canadian capital.

"PM (Harper) was addressing caucus, then a huge boom, followed by rat-a-tat shots. We all scattered. It was clearly right outside our caucus door," Treasury Board Minister Tony Clement said.