Vladimir Putin was sworn in as Russia's president for a fourth term at a ceremony in the Kremlin today, extending his almost two-decade rule by another six years.

"I consider it my duty and my life's aim to do everything possible for Russia, for its present and for its future," Putin said, with his hand on the Russian constitution.

Putin, in power since 1999, was predictably re-elected in Russia's March presidential election with 76.7 percent of the vote.

"I strongly feel conscious of my colossal responsibility," Putin said at the ceremony before thanking Russians for their "sincere support" and "cohesiveness".

"We have revived pride in our fatherland," Putin said.

"As head of state, I will do all I can to multiply the strength and prosperity of Russia." Earlier Russian state television showed Putin walking to the new Russian-made presidential limousine that drove him to the lavish ceremony.