MOSCOW, March 18 -- The result of a referendum held in Crimea was "extremely convincing" and was in accordance with democratic norms, Russian President Vladimir Putin said Tuesday.

Crimea had always been an integral part of Russia, which could not be changed by "time and circumstances," Putin told a joint session of the parliament after he approved a draft agreement between Russia and Crimea on annexing the latter's territory.

As for the legitimacy of Sunday's referendum, Putin said Crimea acted under the UN Chapter which declares the right of a nation for self-determination.

According to Putin, Ukraine lacked legitimate executive power, because the authorities themselves "often work under control from Maidan militants."

Russia could not leave Crimea and its people alone in bad times, otherwise it would be a "treason," he added.

Defending Russian troops' movements in Crimea recently, Putin said they didn't enter Ukraine, as they had already been there in line with the treaty signed between Moscow and Kiev years ago.