Russian television showed three Su-34 fighter planes landing at an air base in the southern part of the country, with pilots in white helmets and aviator jackets mobbed by supporters on their arrival and thrown into the air in celebration. Amid waving Russian flags and red, white and blue balloons, a brass band played the Stalin-era 'March of the Aviators' and the Russian national anthem.

Geneva peace talks

At Syrian peace talks in Geneva, the main Syrian opposition cautiously greeted Putin's troop withdrawal, saying it could lead to an end to five years' of fighting and Syrian President Bashar al-Assad's 'dictatorship and his crimes.'

But Damascus has rejected any notion Assad is willing to relinquish power.

The U.N. special envoy for Syria, Staffan de Mistura, called Putin's announcement a 'significant development' and said he hopes it will lead to 'a peaceful political transition in the country.'

France also expressed cautious optimism, with its foreign ministry saying that if the Russian troop reduction is 'followed up by concrete action, it would be a positive development.'

Some military personnel to stay

Despite the initial withdrawal, Russia plans to keep about 1,000 military personnel at air and naval bases in Syria. The United States has estimated that Moscow has had between 3,000 and 6,000 troops in Syria.

In Syria, deputy defense minister Nikolai Pankov told Russian news agencies, 'It is still too early to speak of victory over terrorism. The Russian air group has a task of continuing to strike terrorist targets.'

Russia's Defense Ministry said Tuesday its first group of planes left Syria following President Vladimir Putin's announcement he was withdrawing most of his forces after a 5½-month operation.

The aircraft left Hmeymim airbase in Syria's western Latakia province to fly back to Russia.

White House reaction

The White House said U.S. President Barack Obama called Putin Monday to discuss Russia's announcement of a withdrawal, and to talk about how to advance the political negotiations for Syria.

In Damascus, the office of Syria's presidency said Assad agreed to Russia's decision, but added that Russia had promised its air force contingent that arrived in late September will not leave the country altogether.

The Kremlin's website quoted Putin as saying Russia would maintain a 'post' for supporting flights of aircraft involved in monitoring compliance with the cessation of hostilities in Syria.

Russia's ambassador to the United Nations, Vitaly Churkin, said Monday that Russia is making this move to withdraw its forces from Syria because 'we are in the political mode now, in the cessation of hostilities mode.'

'Our diplomacy has received marching orders to intensify our efforts to achieve [a] political settlement in Syria,' Churkin said. 'Our forces have operated very effectively. Our military presence will continue to be there; it will be directed mostly at making sure the cease-fire, cessation of hostilities is maintained.'

Syrian opposition spokesman Salim al-Muslat cautiously welcomed Putin's move.

'We have to be sure about the nature of this decision and what it means. If there is a decision to pull troops, then this is positive. We have to see that translated on the ground and whether it's a decision to withdraw troops or to reduce the number of warplanes in Syria,' al-Muslat said.

National Security Correspondent Jeff Seldin and United Nations Correspondent Margaret Besheer contributed to this report.