China is preparing for a once-in-a-decade change of leadership.
The Communist Party Congress, held once every 10 years, opened in Beijing on Thursday.
The week-long meeting will climax with President Hu Jintao standing down and Vice-President Xi Jinping taking his place.
Hu said his successor must make cracking down on graft a priority.
“Combating corruption and promoting political integrity, which is a major political issue of great concern to the people, is a clear-cut and long-term political commitment of the Party,” Hu told delegates.
“If we fail to handle this issue, it could prove fatal to the party, and even cause the collapse of the party and the fall of the state.”
There was a high police presence outside the Congress venue in Tiananmen Square, with authorities restricting the movement of journalists.
In Hong Kong, democracy activists have held their own protests against the Communist Party.
The group gathered outside the Chinese government’s office in Hong Kong, brandishing photos of jailed Nobel Peace Prize winner Liu Xiaobo.