Chelsea fans were ambushed ahead of their Europa League clash with PAOK by a group of locals in the Greek city of Thessaloniki.
The band of four turned violent in the city centre in the early hours of Thursday morning as they attacked two Chelsea supporters at around 5am local time.
The Blues fans were attended to by an ambulance but refused to be taken to hospital following the incident, according to reports in Greece.
The incident occurred at around 5am Greek time at the Tsimiki Street junction, one of the main drags in the Greek port city of Thessaloniki.
It comes on the morning of Chelsea's Europa League opener against Greek outfit PAOK, who will pose a tough test in a hostile environment.
PAOK fans have a reputation for their passionate fans and the intense and hostile atmosphere they produce at the Toumba Stadium.
They have also been known to become violent and on big matchdays will light flares and go to extreme levels to make the opposition feel uncomfortable.
During their recent Champions League qualifier with Benfica, the fans lit hundreds of flares around the ground to create a 'ring of fire'.
Chelsea will have to expect a tough test at the 29,000-seater stadium, but Maurizio Sarri has left his prized asset, Eden Hazard, at home.
England international Ruben Loftus-Cheek made the 1300 mile trip and could be handed a rare start, while rising star Ethan Ampadu also traveled.
SGM17
49
Thats not how real fans behave... supporters are first passionate about the game and then the club. that is why we have rivals giving standing ovations to outstanding players. the four responsible should be banned and the club should be fined to ensure it keeps a closer look on its supporters. We can't allow a few destroy the beautiful game.