CAIRO – Turkey’s military fired on U.S.-allied Kurdish fighters in northern Syria in a bid to keep them from advancing toward the border, the Turkish prime minister said Tuesday.

The comments by Ahmet Davutoglu were the first time that Turkey has confirmed the use of force against ethnic Kurdish militias in neighboring Syria. The Turkish government – which is facing a Kurdish insurgency of its own at home – fears these militias could carve out a breakaway Kurdish enclave along the Turkish-Syrian border amid Syria’s chaotic civil war.

The incident underscored the potential for friction between the United States and its NATO ally Turkey over the Pentagon’s new strategy of providing greater assistance to the Syrian Kurds.

Syria’s main Kurdish militia – known as the People’s Protection Units, or YPG – said that Turkish forces fired on its positions in the northern Syrian town of Tal Abyad on Sunday but that no one was injured and that Kurdish fighters did not return fire, according to the Associated Press.

Turkey has fought a decades-long war with ethnic Kurds seeking autonomy in the southeastern part of the country. Turkish officials are worried that growing Kurdish autonomy in Syria will inspire Turkey’s Kurds to intensify their fight.

In Syria, the YPG has emerged as one of the strongest opponents of the Islamic State. YPG fighters, backed by U.S. airstrikes, routed the Islamic State from Tal Abyad this summer and drove out Islamic State fighters from the strategic border town of Kobane in January.

Washington now says it will increase aid to the Syrian Kurds after U.S. efforts to train other Syrian rebel factions produced few results against the Islamic State. But the cooperation between the U.S. military and Kurdish militants has irked Turkey.

The tensions on Turkey’s border come as Russia’s military intervention to prop up Syria’s government has led to intensified fighting across the country.

On Tuesday, Russia’s Defense Ministry announced that one of its servicemen had died in Syria, the first confirmed death of a soldier there since Russia began its airstrikes last month.

Vadim Kostenko, 19, a soldier servicing Russian warplanes at a base in the port city of Latakia, committed suicide on Saturday, the Defense Ministry told several state news agencies.

But online activists and Kostenko’s parents, who confirmed the death of their son, said that they do not believe that he killed himself.

Kostenko’s parents, speaking to the Reuters news agency, said that he had been cheerful when they spoke with him on the phone Saturday, the day he allegedly killed himself.

“I will never believe this version,” Svetlana Kostenko, the soldier’s mother, told Reuters, referring to the reported suicide.

Meanwhile, in Iran – another ally of Syrian President Bashar al-Assad – a senior commander said his nation plans to boost its military support for the Syrian government, including efforts to upgrade Assad’s forces and assistance in recruiting fighters.

Brig. Gen. Hossein Salami gave no details, but the comments suggest that Iran could increasingly shift some of its proxy Shiite militias in Iraq and Lebanon to provide backup for Assad.

“The 1 / 8Syrian 3 / 8 army has been involved for four years in a draining war. It needs a structural change,” Salami, the deputy head of Iran’s powerful Revolutionary Guard Corps, said in an interview broadcast late Monday, according to the Iranian news agency Tasnim.

Elsewhere, opposition activists reported that Islamic State militants carried out more destruction and killings in Syria’s ancient city of Palmyra, which the group seized in May.

The Islamic State killed three captives in Palmyra by tying them to Roman-era columns and then blowing up the structures with explosives, activists said Tuesday.

A Palmyra activist who goes by the name Nasser al-Thaer told the Associated Press that the execution of the three captives took place on Monday afternoon at the Palmyra archaeological site. Al-Thaer and the Britain-based Syrian Observatory for Human Rights, which relies on a network of activists on the ground, said the three were civilians but that their identities remain unknown.