Russia has confirmed one of its warships fired warning shots at a Turkish vessel in the Aegean Sea to avoid a collision, and has warned Turkey to stop staging what it called provocations against its forces in or near Syria.
The Kremlin said the fishing vessel got within 600 metres of the warship before turning away.
Diplomatic relations have been strained since Turkey shot down a Russian bomber last month.
The Russian Defence Ministry said the destroyer Smetlivy had been forced to fire the warning shots on Sunday morning.
The ministry had summoned the Turkish military attache over the incident.
"The Turkish military diplomat was given a tough explanation about the potentially disastrous consequences from Ankara's reckless actions towards Russia's military contingent fighting against international terrorism in Syria," the Defence Ministry said in a statement.
"In particular, our deep concerns about more Turkish provocations towards the Russian destroyer Smetlivy were conveyed."
Earlier on Sunday, the ministry said that the Turkish fishing vessel failed to respond to Smetlivy's warnings and changed course sharply only after shots were fired before passing within just over 500 metres of the warship.
"Only by luck was tragedy avoided," the ministry said.
Ankara was investigating the matter and would make a statement once it had more information, Turkish Foreign Minister Mevlut Cavusoglu, who was in Rome for talks on Libya, said.
He also reiterated Turkey's position that it wanted to resolve its difficulties with Russia. "We want to solve the tension with dialogue," he said, in comments broadcast by TRT Turk.
The incident is likely to heighten tensions between the two nations who are seriously at odds over Syria and the Turkish shooting down of a Russian military jet last month.
Russian President Vladimir Putin, who called the downing of the plane a "stab in the back", has since imposed economic sanctions on Turkey as a retaliatory measure.
Earlier this month, Turkey complained to Russia over an incident in which a Russian sailor was pictured brandishing a rocket launcher on the deck of a naval ship passing through Istanbul.