Russian Defence Ministry said in a statement on Wednesday that a second group of its warplanes has left the Russian air base in Syria and is returning home.
According to the statement, SU-25 combat aircraft, IL-76 transport planes and several Sukhoi-24 jet bombers pulled out of Russia's Hmeymim Air Base in Syria on Wednesday.
The announcement came two days after Russian President Vladimir Putin ordered Russian military to withdraw most of its fighting forces from Syria, signalling an end to Russia’s air campaign.
The withdrawal from the Hmeymim air base coincides with the resumption of UN-brokered peace talks in Geneva between the Syrian regime and the representatives of the opposition.
Russian Foreign Ministry spokeswoman Maria Zakharova said on Wednesday that the withdrawal of the main part of the Russian armed forces in Syria would not weaken Syrian regime leader Bashar al Assad.
Zakharova added that the main theme of US Secretary of State John Kerry’s visit to Russia would be Syrian conflict next week.
A cessation of hostilities has been in effect since late February. DAESH terrorist group and Al Qaeda-linked Nusra Front are not included in the truce.
Russia did not specify when the next group of planes will leave or how many will be withdrawn.
A first group of the Russian warplanes arrived back in Russian city of Voronezh on Tuesday and Washington said that "the earliest indications are that the Russians are following through" on the surprise withdrawal.
The pullouts have raised hopes for the Geneva peace talks aimed at ending Syria’s brutal five-year conflict, which has killed more than 270,000 people and displaced millions.
UN envoy Staffan de Mistura described the withdrawal as a "significant development" for the talks after the Syrian regime and opposition representatives submitted roadmaps for a political solutions.
"We hope (this) will have a positive impact on the progress of the negotiations," de Mistura said.
Kerry said on Tuesday that he would hold talks with Putin to "try to take advantage of this moment," which he described as the best opportunity in years to end the bloodshed.
"As we mark the fifth anniversary of the start of this horrific war, we may face the best opportunity that we've had in years to end it," Kerry said.
On Monday, Putin ordered the “main part” of Russian forces out of Syria but pledged to keep some air and naval bases in the war-torn nation.
A Russian senior official said that strikes would continue against “terrorist targets”. A monitoring group also said that Russian warplanes had struck DAESH around the city of Palmyra.
Iranian Foreign Minister Mohammad Javad Zarif called Russia’s decision to pull out its forces from Syria “a positive sign” as a senior security official said that the move was pre-planned and not a surprise to Tehran.
"The fact that Russia announced they are withdrawing part of its forces indicates that they don't see an imminent need for resort to force in maintaining the ceasefire," Zarif said during a visit to Australia on Tuesday.
"That in and of itself could be a positive sign. We have to wait and see," he added.
Pressure on Assad
Some governments expressed hope the Russian withdrawal could pressure Syrian regime leader Bashar al Assad to negotiate although Kremlin has denied that was its intention.
German Foreign Ministry said that a Russian withdrawal “increases the pressure” on Assad to negotiate as France was saying "Anything that helps towards a de-escalation in Syria should be encouraged."
Assad’s fate remains a key sticking point in the Geneva talks which are also looking at how to form a new government, a fresh constitution and hold elections within 18 months.
De Mistura said that both parties submitted their views on how to step forward and he would try to “analyse” their positions to find any possible common ground.
"We... exchanged some papers but also ideas on how to get deeper at the next meeting on the issue of transitional processes," the envoy said after the second day of negotiations.
Syrian main opposition group said on Tuesday that it would be ready to negotiate in the same room with the regime instead of via mediator if there was progress.
Almost half of Syrian strike force
Analysis of satellite imagery shows that half of Russia's fixed-wing strike force based in Syria has flown out of the country in the past two days.
According to the analysis and defence ministry statements, Russia kept around 36 military jets at its Hmeymim base in Syria’s Latakia province. At least 15 of those planes, including Su-24, Su-25, Su-30 and Su-34 jets, have taken off for Russia in the past two days.
Russia is also believed to maintain at least 14 military helicopters as well as fixed-wing reconnaissance drones at the base. If they are pulled out, the helicopters are likely to be shipped out by sea or by air.