Chinese state media reported that a "car accident" in central Beijing's Tiananmen Square has left five people dead.
However, comments on Chinese social media disputing the official version of events are being deleted by the authorities.
ITV News China Correspondent Angus Walker reports.
Chinese authorities were calling it a car accident. But now they are hunting suspects in what could be Beijing's first major suicide attack.
There is clearly a security operation underway to deal with what state media has been calling an accident.