MOSCOW -- Russian President Dmitry Medvedev renewed his calls to modernize his country's oil-dependent economy and open up the political system but gave no sign the Kremlin plans to loosen its tight control.

"The strengthening of democracy does not mean the weakening of law and order," Mr. Medvedev said Thursday in an annual address to parliament and top government officials. "Any attempts to rock the situation under democratic slogans, to destabilize the state and split society will be stopped."

On...