The Chinese government suspects that an incident in which a vehicle ploughed into pedestrians in Beijing's Tiananmen Square was a suicide attack.
Five people were killed, including three people in the vehicle.
A further 38 people were injured in the incident, but there has been no official word whether it was an accident or an attack.
"It looks like a premeditated suicide attack," a source with direct knowledge of the matter said.
Police are still investigating and have yet to determine the identities of the three people in the vehicle.
Beijing police said they were looking for two suspects from the far western region of Xinjiang in connection with a "major incident".