Russian President Dmitry Medvedev has warned that "provocateurs and extremists" will not be permitted to "divide Russian society".
His comments, in his state-of-the-nation address, followed mass demonstrations in Moscow and other major Russian cities.
Russia needs democracy, not chaos, he said, and warned that his government would resist any foreign pressure.
His statement came in the wake of mass rallies against alleged fraud and vote-rigging in the 4 December parliamentary elections, in which the Kremlin's United Russia party barely held on to its majority.
"Attempts to manipulate Russian citizens, to confuse them, stir up divisions in society, are unacceptable," Medvedev said.
"We won't let provocateurs and extremists drag society into their adventures."
Another large opposition rally is expected this weekend amid continued demands for a re-run of the disputed election.
The president, who is widely seen as one of Prime Minister Vladimir Putin's puppets, also proposed "comprehensive" political reforms, including simplifying the procedure for registering political parties and for the direct election of regional governors.
"We must give all active citizens the opportunity to take part in political life," he said. "The presidential elections must be honest, transparent, and respond to the requirements of legality and justice."