Shots are reported to have been fired outside the Israeli embassy in Athens by two men riding a motorbike.
No injuries have been reported so far. The embassy building is located at a corner of a busy highway, which has been closed following the event.
Local reports said the two men on the bike who opened fire were joined by another duo on a motorbike. The incident took place at around 3:20am local time.
The police said that Kalashnikov assault rifles were used by the perpetrators, according to AFP. Greek forensic officials are examining the bullet castings recovered from the scene.
Embassy officials are also reportedly taking part in the investigations.
There has been increasing condemnation in Greece of Israel's settlement policies in the West Bank and Gaza by pro-Palestine protesters.
In 2012, a similar attack took place outside the Israeli embassy in New Delhi in which a diplomatic staff member's wife was injured.