Russia's Foreign Ministry on Tuesday voiced concern about the reported bombing of a Syrian army camp, without addressing a U.S. claim that Russia was responsible for the incident.
The Syrian government blamed aircraft from a U.S.-led coalition for targeting the army camp in the eastern city of Deir el-Zour Sunday night, killing three Syrian soldiers and wounding 13.
The U.S. denied the claim, and a senior U.S. official military said Monday Washington was "certain" it was a Russian airstrike that hit the camp. The official spoke on condition of anonymity because he wasn't authorized to discuss the issue publicly.
Without commenting on the U.S. claim, Russia's Foreign Ministry on Tuesday said it has a "serious concern" about reports of the coalition strike in Deir el-Zour. It said the incident was rooted in the U.S.-led coalition's reluctance to coordinate with Damascus on its campaign against the Islamic State group.
The ministry also mentioned a coalition strike in Syria's province of Hassake that reportedly involved civilian casualties.
"These incidents show that the situation on the front against the IS in Syria and Iraq is exacerbating," the ministry said, adding that the Turkish military's deployment to a base near Mosul in Iraq without Iraqi government sanction has added to the tensions.
"We consider such presence unacceptable," the ministry said.
Moscow's relations with Ankara have been badly strained over Turkey's downing of a Russian warplane at the Syrian border. Turkey said it shot down the plane after it violated its airspace for 17 seconds despite repeated warnings, while Russia insisted that the aircraft had stayed in Syria's airspace.
Russia has responded by deploying long-range air defense missiles at its air base in Syria and introducing a slew of economic sanctions against Turkey.
Russian Foreign Ministry spokeswoman Maria Zakharova dismissed Turkey's complaint about a sailor on board a Russian navy vessel who was pictured on its deck with a portable air-defense missile while the ship was cruising across the Bosporus.
Turkey denounced the incident as a provocation and summoned the Russian ambassador to protest. Zakharova responded Tuesday by saying that the Russian crew had the right to protect its vessel. She insisted that the action didn't contradict the Montreux Convention, which sets out international rules for using the Turkish straits.
On Tuesday, Russia's Interfax news agency reported that a Russian submarine equipped with long-range cruise missiles has deployed to an area near the Syrian shore.