Police clashed with firefighters during a protest rally by the latter outside the Ministry of Climate Crisis and Civil Protection in Athens.
According to reports, the police fired tear gas and flash grenades and deployed a water cannon against the firefighters.
Traffic on Kifissias Ave, where the protest took place, was halted for about 20 minutes.
Police later said they made five arrests. Reports say a forest firefighter was injured.
About 2,000 seasonal firefighters from all over Greece took part in the demonstration, which was staged to demand that they be made permanent.