(CNN)Pro-Syrian government fighters entered the contested region of Afrin on Tuesday and were reportedly fired on by Turkish forces, risking further military escalation between the two countries.
Pro-Syrian regime forces enter Afrin to support Kurdish fighters
The pro-regime "popular forces" were deployed to support Kurdish fighters who hold Afrin in northwest Syria but are under attack from the Turkish military, according to Syrian state news.
During a press conference in Ankara Tuesday, Turkish president Recep Tayyip Erdogan said that pro-Syrian forces pulled back after coming under fire from Turkish troops.
"They [pro-Syrian forces] were forced to go back after artillery shooting," Erdogan said, adding "terror organizations" must "pay a heavy price" when taking "wrong steps."
During a live broadcast, a reporter for Syrian state TV said Turkish forces had targeted the pro-government forces' units and that mortars could be heard in the background.
Syrian state TV showed dozens of armed men in military uniforms waving the Syrian national flag alongside a convoy of trucks loaded with machine guns.
Turkey's deputy prime minister warned Syria on Monday of "disastrous consequences" should the Syrian government send forces to support the Kurdish fighters. Ankara considers them to be terrorist groups linked to an insurgency inside its own borders.
Three Kurdish militias -- the Kurdish Democratic Union Party (PYD), the People's Protection Units (YPG) and the Kurdistan Workers' Party (PKK) -- have borne the brunt of the month-long offensive Turkey launched in Afrin to clear the border of the groups, along with ISIS militants still remaining on the battlefield.
On Tuesday the YPG said the Syrian government had "answered our call" to send troops to defend Afrin against "the Turkish invasion".
"After a month of our forces' epic resistance to the Turkish invasion and the terrorist organization allied with it," the YPG invited the "Syrian government and its army to perform its duty by participating in defending Afrin and protecting the Syrian borders," the YPG said in a statement.
"The Syrian government has answered our call ... and sent military units on Tuesday, February 20th to be stationed along the borders and to help in defending the unity of the Syrian territories and its borders," the statement added.
The deployment of pro-regime forces to Afrin complicates an already fraught conflict in the Kurdish regions of northern Syria.
It essentially places the YPG -- allies with the US in the fight against ISIS -- on the same side as forces loyal to Syrian President Bashar al-Assad, who the US opposes.
Turkish Foreign Minister Mevlut Cavusoglu said Monday that Turkey had no intention of suspending operations in Afrin, and questioned the value of any Syrian government deployment to the area.
"If they do go in, what are they [the Syrian forces] going in to do? That is what is important. If the regime goes in to clear the PKK/YPG then there is no problem. But if the regime is going to protect the PKK/YPG then we, Turkey and Turkish soldiers, cannot be stopped," Cavusoglu said at a news conference in Amman.
Afrin has sustained relentless attacks from Turkey since January 20, when Ankara launched a campaign called Operation Olive Branch.
Turkey sees the quest by the Kurds -- who are spread out in Turkey, Syria, Iran and Iraq -- to establish an independent homeland as an existential threat to its territorial integrity. And Turkey has long warned that it will not tolerate YPG control of much of its border with Syria.
An estimated 16,000 people have been displaced by the fighting, which has been punctuated by relentless airstrikes and shelling, according to the United Nations.
A US announcement in mid-January that it would form a 30,000-strong Kurdish-led border force in northeastern Syria also sparked this heightened period of US-Turkey tension.
According to a readout from the Kremlin, Russian President Vladimir Putin and Turkish President Erdogan discussed the Turkish operations in Afrin, but offered few details on Monday's call.
It also said that the Russian and Turkish leaders continued to promote their own Syrian peace talks effort -- together with Iran -- in Astana, Kazakhstan, over anything the UN-sponsored talks in Geneva might produce.
Noting the "positive dynamics in the development of Russian-Turkish cooperation," the Kremlin said that "special attention was paid to the further strengthening of the interaction in the Astana format."
"The readiness for close coordination of the efforts of Russia, Turkey and Iran was confirmed with a view to ensuring the effective functioning of the de-escalation zones and the promotion of the political process," the Kremlin statement said.
Last month, Russian Foreign Minister Sergey Lavrov was heckled during his speech at a Russia-engineered peace conference at the Black Sea resort of Sochi. The conference was snubbed by many opposition figures, and some of those who actually attended walked out during Lavrov's address.
Organizers of the summit had hoped the talks would lead to a new draft constitution for Syria and bring an end to sanctions imposed on the state.