Moscow (dpa) - Russian President Dmitry Medvedev Tuesday signed into law a bill extending presidential terms form four to six years, the Kremlin said.

Medvedev final endorsement of the constitutional amendment follows rapid legislative approval by both Russian houses parliament as well as 83 regional chambers.

The Kremlin pushed hard to fast-track the amendment - the first to Russia's 15-year-old constitution - through the constitutional process.

It has been less than two months since Medvedev proposed the constitutional changes in his first state-of-the nation speech on November 5.

The law will apply only to the next elected president, legal experts said. Critics charge the law is aimed at paving the way for Prime Minister Vladimir Putin's return to the Kremlin for what could now be 12 more years.

Putin ceded the presidency to his handpicked successor Medvedev in May as the constitution barred him from a third consecutive term. He has not ruled out standing for another term. (dpa)