Greek police used tear gas on Sunday against demonstrators opposing the “Macedonia” name deal in central Athens.
A group of around 30 demonstrators threw rocks and flares against the police in Syntagma square, opposite the Greek parliament, after the end of a peaceful rally against the deal.
Police made three arrests.
Scuffles also broke out in a similar rally in Thessaloniki, Greece’s second largest city.
Protesters had originally tried to gather in front of the White Tower but were prevented from doing so by police. There were some brief scuffles before the protesters moved their rally on to Aristotelous.
Greece and FYROM signed a pact this month to rename the former Yugoslav state North Macedonia to end decades of dispute between them, but the move has fuelled protests on both sides of the border.