Turkey has accused Russia of “provocation” after a Russian navy serviceman allegedly held a rocket launcher on his shoulder as his ship passed through Istanbul.
Relations between the two countries have been on tenterhooks since Turkey downed a Russian plane it said violated its airspace on 24 November.
And at the weekend, Turkish television channel NTV broadcast images showing a serviceman with the high-powered weapon on the deck of the landing ship Caesar Kunikov as it passed through the Bosphorus Strait - which runs through Istanbul.
The ship was believed to be on its way to Syria.
Speaking to Turkish news website Hurriyet, Turkish foreign minister Mevlut Cavusoglu said: "For a Russian soldier to display a rocket launcher or something similar while passing on a Russian warship is a provocation.
"If we perceive a threatening situation, we will give the necessary response."
The incident is the latest in a string of escalating diplomatic moves between the two countries after the plane was downed.
Turkey claims it gave Russia 10 warnings when the jet violated Turkish airspace - but Russia insists this is “rubbish”.
The plane landed inside Syrian territory.
The diplomatic row escalated further last week when Vladimir Putin accused Turkey of buying oil from Isis.
Moscow published satellite images it said showed Turkish tanker trucks filling up at an oil station controlled by Isis in Syria.
In response, Turkish president Recep Tayyip Erdogan claimed they had evidence Russia was buying oil from the jihadist group.
Additional reporting by Reuters
