Security forces have been deployed in force across Beijing, ahead of a military parade expected to showcase previously unseen missile technology.
A pageant featuring ordinary people will also be held in Tiananmen Square.
Some 30,000 people have been invited to watch the events, but others are being encouraged to stay at home and watch it on TV to "avoid complications".
Armed police in body armour have taken up positions at major road junctions in the capital, with snipers spotted on buildings along the parade route on Chang'an Avenue.
The BBC's Michael Bristow in Beijing says roads have been blocked off, the international airport will be closed and the subway disrupted.
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