"This is not a meeting. This is not a demonstration," organisers of the "Great White Ring" event said in their Facebook account.

"On this day, we will gather without signs, slogans or speeches. We will stand and be silent, shoulder to shoulder, hand in hand."

The group said it would take 34,000 people to join hands around Moscow's 16-kilometre (10-mile) busy thoroughfare. It had 13,000 volunteers signed up on Facebook and more than 36,000 on the page's Russian counterpart Vkotnakte.

The event was scheduled to begin at 2:00 pm (1000 GMT). Moscow authorities have not granted official authorisation for the action but organisers say it is legal as long as participants stay silent while linking hands.

The Russian strongman's supporters planned to fight back by staging their own event on a central Moscow square called "Putin Loves Everyone".

A Kremlin youth group said it would hand out ribbons with the Russian tricolour flag -- a clear reference to the white ones worn by the opposition -- throughout the afternoon and take pictures of Putin's supporters.

Russia has witnessed more than a month of weekly rival rallies between Putin's foes and his state-backed supporters in advance of elections that the 59-year-old former KGB spy is almost certain to win.

The latest polls and forecasts show Putin winning in the first round with around 10 percentage points fewer than the 71 percent he secured on his re-election to a second term in 2004.

The protest action echoes a historic human chain that the three tiny Baltic states organised in 1989 to demand their independence from the Soviet Union.

More than a million people were estimated to have taken part in a protest that was followed in the subsequent two years by their declarations of independence.