A 19-year-old woman was being treated in a hospital in the city of Ioannina, in western Greece, on Wednesday after she was hit in the face by an object during an anti-fascist march in Agrinio to commemorate a 36-year-old rapper killed by a self-professed member of Golden Dawn five years ago.
The teenager was not participating in the rally but was sitting on a bench with a friend during the protests.
The exact circumstances of her injury are not clear, with some claiming she was hit by a stone and others by an improvised naval flare which caused her to lose consciousness. Eye-witnesses said she was bleeding profusely after the accident.
She is expected to undergo surgery on Wednesday but her life is not at risk.
Local police has opened an investigation to locate the perpetrators and filed charges against unknown individuals for causing bodily harm.
Six people were arrested and 25 detained during clashes with police on Tuesday night but so far none of them appears to be linked to the injury of the 19-year-old.
Those arrested appeared before the prosecutor in Agrinio on Wednesday morning.
Similar rallies in Piraeus and Thessaloniki in memory of Pavlos Fyssas on Tuesday night were marked by skirmishes with police, who fired teargas against protesters.
In Piraeus, a group of unknown individuals threw petrol bombs and stones against a riot police van stationed next to the Municipal Theatre, to block access to the offices of Golden Dawn.
Similar scenes developed in Thessaloniki, where a group of masked youths attacked riot police officers guarding ruling SYRIZA's offices with petrol bombs.