A Russian SU-34 jet has violated Turkish airspace despite radar warnings, Turkey's foreign ministry said, and the Russian ambassador was summoned over the incident.
The ministry said in a statement on Saturday that the violation, which allegedly occurred on Friday, was a clear sign that Russia wanted issues between the two countries to escalate.
The Russian defence ministry dismissed the allegations as "baseless propaganda".
"There has not been a single violation of Turkish airspace by Russia air force planes in Syria," ministry spokesman Igor Konashenkov told Russian news agencies.
However, Turkey's President Recep Tayyip Erdogan insisted that a Russian jet breached the skies over his country and warned Russia of "consequences" if it continued to violate Turkish airspace.
"The airspace that is violated is not only Turkish airspace but NATO's as well," Erdogan said.
"So NATO is closely watching the situation. NATO even detected this violation before we did. If Russia continues to violate Turkey's sovereignty, has to put up with the consequences. I suggested talking with (Russian President Vladimir) Putin but he didn't come back to me by phone..."
NATO Secretary General Jens Stoltenberg urged Russia to "take all necessary measures" to ensure the bloc's airspace was not violated again.
"A Russian combat aircraft violated Turkish airspace yesterday, despite repeated warnings by the Turkish authorities. Previous incidents have shown how dangerous such behaviour is," Stoltenberg said in a statement.
"I call on Russia to act responsibly and to fully respect NATO airspace."
Russian warplane shot down near Turkey-Syria border
Turkey shot down a Russian warplane in November in an incident that wrecked relations between the two countries, both of which are involved in Syria's war.
The Russian defence ministry acknowledged that an Su-24 fighter jet crashed in Syria as a result of fire from the ground but said the plane had stayed within Syrian airspace and that "objective monitoring data confirm this".
