Russian President Vladimir Putin has signed a law on constitutional changes that could keep him in power for another 16 years, a step that must still be approved in a nationwide vote.

Putin signed the measure on Saturday, the Kremlin said, three days after it sailed through the Russian parliament with only one vote against. It must be approved by the country's Constitutional Court and in a referendum set for April 22.

Under current law, Putin would not be able to run for president again in 2024 because of term limits, but the new measure would reset his term count, allowing him to run for two more six-year terms. He has been in power since 2000.

Other constitutional changes further strengthen the presidency and emphasize the priority of Russian law over international norms – a provision reflecting the Kremlin's irritation with the European Court of Human Rights and other international bodies that have often issued verdicts against Russia.

The changes also outlaw same-sex marriage and mention "a belief in God” as one of Russia's traditional values.