Russian forces have started leaving Syria after Monday's surprise withdrawal announcement by President Vladimir Putin.
Russian defence ministry video showed the first group of aircraft taking off from Hmeimim air base in Syria on Tuesday morning and later in flight.
But Russia will continue air strikes, and keep several hundred personnel and air defence systems, officials said.
Peace talks aimed at resolving the conflict are entering a second day.
UN Special Envoy Staffan de Mistura, who is mediating in the talks, welcomed the Russian decision.
"The announcement by President Putin on the very day of the beginning of this round of Intra-Syrian Talks in Geneva is a significant development, which we hope will have a positive impact on the progress of the negotiations," he said.
The Russian force reduction was announced during a meeting between Mr Putin and his defence and foreign ministers.
Russia is a key ally of Syrian President Bashar al-Assad, and his office sought to reject speculation there was a rift between the two countries, saying the move was mutually agreed.
More on the Syria conflict
The Russian air campaign started last September, tipping the balance in favour of the Syrian government and allowing it to recapture territory from rebels, but on Tuesday the defence ministry announced the withdrawal.
"The first group of Russian planes has flown out of the Hmeimim air base for their permanent bases on the territory of the Russian Federation," it said in a statement (in Russian).
Aircraft from the base would make the flight to Russia - more than 5,000km - in small groups each led by Il-76 or Tu-154 transport planes, the statement said.
They would then go their separate ways to their own bases after crossing the Russian border, it added.
Su-24 tactical bombers, Su-25 attack fighters, Su-34 strike fighters and helicopters were returning home, the TV said.
Mr Putin, however, said Hmeimim and Russia's Mediterranean naval base at Tartous would continue to operate as normal.
Deputy Defence Minister Nikolay Pankov said some air strikes would continue.
"Certain positive results have been achieved... However, it is too early to talk about victory over terrorism. A Russian air group has the task of continuing to strike terrorist facilities," he said, quoted by Ria news agency.
Bigger game: BBC's Lyse Doucet in Damascus
Russia's military intervention bolstered president Assad's forces on key front lines where they were close to collapse.
Russia now wants to see an end to this war - and it is known to be concerned about the Syrian government's tough line on talks which have just resumed in Geneva, as well as president Assad's recent comments in an interview that he would one day take back, militarily, all the territory he lost.
That is not a war president Mr Putin can afford to be part of.
And he has a bigger game here - his wider relationship with the West and most of all Washington which is also anxious to find a way out of this crisis in Syria - as hard as that is.
Another senior official, Federation Council defence committee head Viktor Ozerov, said as many as two battalions - some 800 servicemen - could remain in Syria after the withdrawal to guard the two bases, Interfax news agency reported.
Military advisers training Syrian government troops would also stay, he added.
Meanwhile Kremlin chief-of-staff Sergey Ivanov said Russia would keep its advanced S-400 surface-to-air missile system in place.
"We are leaving completely reliable cover for the remaining contingent... To effectively ensure security, including from the air, we need the most modern air defence systems," Russian media quoted him as saying.
It is not clear how many military personnel Russia has deployed, but US estimates suggest the number ranges from 3,000 to 6,000, AP reports.
Russia had long insisted its bombing campaign only targeted terrorist groups but Western powers had complained the raids hit political opponents of President Assad.
In a statement, the Syrian government said the plan was agreed between the two countries.
What did Russia achieve in Syria?
- Russian aircraft flew more than 9,000 sorties
- Destroyed 209 oil production and transfer facilities
- Helped Syrian government troops to retake 400 settlements
- Helped Damascus to regain control over more than 10,000 sq km (3,860 sq miles) of territory
Source: Russian Defence Minister Sergei Shoigu, quoted by Russian media
Most participants in the Syria conflict agreed to a cessation of hostilities, which has been largely holding despite reports of some violations on all sides.
Meanwhile, the UN Commission of Inquiry on Syria has presented its report on war crimes committed by all sides in Syria's war to the UN Human Rights Council in Geneva.
Its chairman Paulo Pinheiro said the task of pursuing war criminals should not wait for a final peace agreement as there was now "hope of an end in sight".
In a phone call, Mr Putin and US President Barack Obama discussed the situation in Syria and the "next steps required to fully implement the cessation of hostilities" agreed last month, the White House said.
The Kremlin said both "called for an intensification of the process for a political settlement" to the conflict.
The Russian move has received a guarded welcome from Western diplomats and the Syrian opposition.
An unnamed US official quoted by Reuters said Washington was encouraged by the Russian move, but it was too early to say what it means or what was behind it.
Why did Russia launch an air campaign in Syria?
Russia is one of President Bashar al-Assad's most important international backers and the survival of his government is critical to maintaining Russian interests in Syria. Russia has a key naval facility which it leases at the port of Tartus and has forces at the Hmeimim airbase in Latakia.
In September 2015, with rebel forces advancing on Latakia, Russian forces launched an air campaign which President Vladimir Putin said was aimed at "stabilising" the Syrian government and creating conditions for "a political compromise" that would end the five-year conflict.
What does Russia say its intervention achieved?
In March 2016, Mr Putin ordered the "main part" of Russia's forces to withdraw from Syria, saying their mission had "on the whole" been accomplished.
Defence Minister Sergei Shoigu said Russian aircraft had flown more than 9,000 sorties over almost six months, killing more than 2,000 "bandits" and helping Syrian government forces regain control of 10,000 sq km (3,860 sq miles) of territory, including 400 population centres.
The claims have not yet been independently verified, but it is clear the air campaign turned the tide of the war in favour of Mr Assad, allowing Syrian government ground forces to regain territory around Latakia, in the southern province of Deraa and around the divided northern city of Aleppo.
What do critics say?
Moscow stressed that its air strikes only targeted "terrorists", but activists said Russian aircraft mainly bombed Western-backed rebel groups and civilian areas.
In December, Amnesty International said Russian aircraft appeared to have directly attacked civilians by striking residential areas with no evident military target, which it warned might amount to war crimes. Russia's defence ministry dismissed the report as containing "fake information".
However, the UK-based Syrian Observatory for Human Rights reported in early March that 1,733 civilians, including 429 children, had been killed in Russian air strikes, along with some 1,492 rebels and members of the al-Qaeda-affiliated al-Nusra Front, and 1,183 Islamic State (IS) militants.