Russia has denied that it is setting up a new military base in northwestern Syria in Afrin, a region controlled by the YPG.
The YPG is a Syrian affiliate of the PKK, considered a terrorist organisation by Turkey, the US and the EU. However, the US is backing the YPG in Syria, where it considers the group a key ally in its fight against Daesh.
The YPG controls swathes of land in northeastern Syria. Afrin is a YPG-controlled enclave in the northwest and separated from the YPG-controlled northeastern region by Turkish-backed forces as part of its Operation Euphates Shield.
Turkey has threatened to attack YPG forces if they counter Euphrates Shield, which is an effort by Turkey to secure its border with Syria and rid its border region of terror groups.
The YPG on Monday said it had agreed with Russia to set up what it called a "military base" in northwestern Syria under a bilateral agreement and would help train its fighters.
The YPG said Russian troops had arrived in Afrin with troop carriers and armoured vehicles. The Syrian Observatory for Human Rights (SOHR) said some 100 Russian soldiers had entered the Afrin region.
Russia's defence ministry has denied the report. It said it had no plans to open any new military bases in Syria. It said a branch of its "reconciliation centre," that negotiates local truces between the warring sides in Syria, had been located in Aleppo province near Afrin.
Russian MoD refuted information published by foreign media about deployment of 'a new Russian military base' https://t.co/M5NW1mjGTD— (@mod_russia) March 20, 2017
Asked about Afrin, Turkish Deputy Prime Minister Numan Kurtulmus said Ankara would never allow what he called a "terror region, a terror state" to be established in northern Syria, in reference to the YPG.
"We have conveyed this to all interested parties in almost every meeting. The Russians know this, and the Americans know this and other countries know this," Kurtulmus said during a news conference in Ankara.
Helped by allied FSA groups, Turkey has been waging an offensive in northern Syria to stop the YPG creating a contiguous territory along most of its border with Syria.
The YPG also said on Monday it planned to expand its force by about two thirds to more than 100,000 fighters this year with the aim of turning it into a more organised force that resembles a traditional army.