MOSCOW - RUSSIA'S parliament on Friday approved constitutional changes extending the length of presidential terms, a move opponents said could lead to the return of Vladimir Putin to the presidency.

The State Duma approved the extension of presidential mandates from four years to six in a first reading, with 388 votes in favour and 58 against.

The changes 'fully accord with international practice' and will 'increase the period in which state institutions work most fruitfully,' said Mr Vladimir Pligin, head of the Duma's constitutional affairs committee.

The changes, the first ever to Russia's 1993 constitution, were announced earlier by President Dmitry Medvedev and were expected easily to win approval from the overwhelmingly pro-Kremlin parliament.

They will also increase parliamentary terms from four years to five.

Final approval requires the assent of both houses and of two-thirds of Russia's regional assemblies.

The changes have sparked fresh speculation that Medvedev, who succeeded Mr Putin as president in May, could use the pretext of constitutional changes to step down early and make way for a return to the post by his mentor.

Both men have played down such claims without rejecting them outright.

Activists from the opposition Yabloko party mounted a small rally outside parliament, holding up a placard with a quote from Mr Putin, 'You should change brains, not the constitution,' the Echo of Moscow radio station reported.

A deputy prime minister, Igor Shuvalov, has denied the changes are intended to strengthen the presidency, saying 'it should be seen as a balanced model for a new political construct.'

Predicting economic turmoil ahead for Russia, Mr Vladimir Ryzhkov, a commentator and former opposition deputy, said in Friday's Moscow Times newspaper 'Mr Putin might try to keep a step ahead of the game once again.

'Using pretexts such as the new constitution and the need to strengthen the state in the face of the crisis, he might through Medvedev announce snap presidential and parliamentary elections as early as March or April.'

Voicing support on Wednesday for the changes, Mr Putin insisted they had no 'personal dimension'.

He added, 'As far as who could run for the next term or when, it's too early to say'. The response raised eyebrows as it suggested doubt about the next scheduled presidential election date of 2012.

Mr Medvedev was cagey when asked about his intentions in an interview with France's Le Figaro newspaper published on Thursday.

'I'm still working. Why are you trying to push me into some kind of decision? I can only say for sure that this new term can only apply to a presidential candidate who stands for the post after the passage of the corresponding changes,' Mr Medvedev said, according to a Kremlin transcript. -- AFP