Greek and Turkish vessels collided off the Greek islet of Imia in the south-eastern Aegean on Wednesday.
According to Greek defense sources, the incident involved two coast guard vessels and it occurred in Greek territorial waters.
The Greek speedboat from was damaged, the same sources say.
Athens has been downplaying the incident, although an official statement is expected sometime on Thursday.
The circumstances surrounding the collision remain sketchy, with some Turkish news outlets saying that it happened when Greek fishing boats were in the area.
According to the Turkish website anterhaber.com, the Turkish Coast Guard vessel tried to stop Greek fishing boats, leading to the intervention of the Greek speedboat.
It was during the standoff between the vessels that the collision occurred.
Turkey disputes sovereignty
Imia is a pair of small, uninhabited islets, situated between the Greek island chain of the Dodecanese and the southwestern mainland coast of Turkey.
They were the object of a military crisis and subsequent dispute over sovereignty between Greece and Turkey in 1996.
The European Union backed the Greek side in the Imia dispute, and warned Turkey to refrain from any kind of threat or action directed against the sovereignty of Greece.
There have been several tense incidents involving ships from Greece and Turkey in the Aegean.
In 2018, a Turkish Coast Guard vessel rammed into the Greek patrol boat “Gavdos” near Imia.
The dramatic footage was captured on video: