The possible increasing role of Russia in the military future of Syria came into dispute Tuesday after Moscow denied a claim by Kurdish forces that Russia is building a military base in a predominately Kurdish town in northwestern Syria.
Kurdish commanders say Russian forces will be training local Kurdish fighters for the war on Islamic State. Russian troops already have deployed recently near the northwestern town of Afrin, with troop carriers and armored vehicles in support of the Syrian government, Kurdish military officials say.
Kurdish People's Protection Unit (YPG) commanders said the move came after a deal was reached between them and Moscow over the weekend.
"It is the first of its kind," Redur Khalil, a YPG spokesperson, told Reuters news agency.
A video posted Tuesday by the Russian government-controlled Sputnik news agency showed Russian soldiers and tanks in Afrin.
But Russian defense officials said Tuesday that the troops are there only as part of a Russian "reconciliation center" that helps arrange local cease-fires between warring sides in the war-ravaged country. The Kremlin says it has no plans to establish a military base.
Russia, a longtime backer of Syrian President Bashar al-Assad, has been involved in the Syrian civil war since it began in 2011.
Moscow's official military engagement in the conflict began in late 2015, when Russian warplanes launched a massive aerial campaign, targeting Syrian rebel groups throughout the country.
Russia's intervention helped in propping up Assad's forces, particularly in the battle of Aleppo, where government forces and their allied militias pushed out rebel fighters in December 2016.
The Kurdish YPG is the main force within the Syrian Democratic Forces (SDF) that has the U.S. backing in the fight against IS militants. However, Kurdish officials say it is natural to have military ties with Russia as well.
"Russia is a major actor in the [Syrian] conflict," said Khabat Shakir, a YPG official. "So it's very normal for the YPG to strike deals with the Russians in order to guarantee the safety of our people."
The Kurdish forces' ability to garner support from both Washington and Moscow leaves Turkey looking increasingly concerned. Ankara considers the YPG to be a terrorist organization tied with the Turkish-based Kurdistan Workers' Party (PKK), which has been fighting a bloody war against the Turkish military.
In response to the recent development in Afrin, Turkish Deputy Prime Minister Numan Kurtulmus said his county would not allow a "terror region, a terror state" to be established in northern Syria, referring to the Kurdish YPG.
"The Russians know this, and the Americans know this and other countries know this," Kurtulmus told reporters in Ankara.
The U.S., too, has built at least two military bases in the Kurdish-held region of northern Syria, where nearly 1,000 American advisers have been trying to enlist local fighters in the war against IS.
But analysts say that having a Russian presence in the Kurdish region doesn't breach any international laws.
"Russia has been in Syria at the request of the [Syrian] government," said Abdullah Imam, an international law expert and lawyer. "Afrin is part of Syria, and Syria is a member of the United Nations, so technically Russia's military presence there is legal."
As part of the SDF, the YPG has been one of the most effective forces fighting IS across northern Syria. With the support of U.S.-led airstrikes, the group in recent weeks has been advancing toward Raqqa, the de facto capital of IS.
VOA's Saleh Damiger and Henry Ridgwell contributed to this report.