Political parties on Sunday evening condemned an attack on SYRIZA MP for Messinia, Petros Konstantineas, near the Kalamata soccer ground.
The attack on Konstantineas occurred near a bar frequented by Kalamata fans.
The MP told the Athens-Macedonia News Agency that he was set up by around 30 people, apparently members of far-right groups, who beat him.
Konstantineas was taken to Kalamata hospital for treatment to injuries that were not believed to be serious and was expected to be discharged late on Sunday night.
According to sources, the local police detained five people for questioning in connection with the beating and have launched an investigation.
In a statement, the office of Prime Minister Alexis Tsipras said that the "fascists" who attacked Konstantineas would be found and brought to justice.
"That goes for the physical perpetrators. The moral instigators who invest in nationalism and divisive rhetoric with the aim of winning some votes from the far-right should eventually face up to their responsibilities."
Conservative New Democracy also condemned the attack "categorically," saying that "such behavior has no place in a well-governed democracy."