The "emergency" occurred during the opening of China's Communist-controlled National People's Congress on Wednesday, the state-run People's Public Security News said in a report carried on a central government website.
The report gave few details but said that the incident occurred in the "Tiananmen area" at 10.45am, as Chinese Premier Li Keqiang was giving his "work report" on government activities in the Great Hall of the People, which flanks Tiananmen Square.
Later that day China's vice-minister of public security presented the two police with awards for dealing with the incident, the report said, without giving any further details.
Tiananmen Square is the symbolic heart of the Chinese state and always subject to strict control, with many security personnel equipped with fire extinguishers.
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Beijing usually sees a spike in Chinese citizens with grievances against the authorities trying to travel to the capital to lodge formal complaints during the annual Congress meeting.
Beijing police did not respond to phoned and faxed requests for comment on the incident when contacted by AFP.