Police and demonstrators clashed in Athens' Syntagma square on Sunday, as tens of thousands protested against the naming of Greece's northern neighbour as "Northern Macedonia."

Protesters were seen hurling petrol bombs and stones towards law enforcement officials, with police responding with tear gas.

The clashes took place outside parliament in Athens Sunday, where protesters waved flags and chanted slogans including “Macedonia is Greece” and “Hands off Macedonia” against a landmark name deal with neighbouring Macedonia.

The small Balkan country has agreed to change its name from the “Republic of Macedonia” to the “Republic of Northern Macedonia” under the deal between the two nations.

“Giving away the name Macedonia means giving away our land. The aim of the protest rally is to send a message to politicians. Our name is our soul,” Giorgos Tatsios, a member of the rally's organizing committee, said.

Giorgos Golas, 46, who travelled to Athens for the day to attend, said living in the northern Greek town of Ptolemaida made him feel “vulnerable.”

“We don't want an agreement that does not protect us from minority issues being raised or territorial claims.”

Police say 60,000 people have taken part in the rally, ahead of the vote in Parliament — that could take place as early as next week — expected to ratify the agreement. The battle is going to be intense with virtually all opposition parties against the deal.

Greek Prime Minister Alexis Tsipras said it was a “patriotic duty” to proceed with the agreement, despite the political cost.

Both countries are under pressure to resolve the dispute, as Western countries see the integration of Balkan countries into the EU and NATO as a way of improving the region's stability. Greece, a member of the two, has refused to allow Macedonia to be included due to the name dispute. Moscow openly opposes Macedonia's NATO and EU aspirations.