Protests turned violent Sunday between Greek demonstrators and police as tens of thousands of people converged on Athens to oppose a name-change deal with Macedonia.
Greece has long protested the name Macedonia, adopted by its northern neighbor after it split from Yugoslavia.
Greeks say Macedonia's new name -- the Republic of North Macedonia -- represents an attempt to appropriate Greek identity and cultural heritage, because Macedonia is also the name of Greece’s northern province made famous by Alexander the Great's conquests.
The protests Sunday started out peacefully but later in the day demonstrators threw rocks, firebombs and other items at police, who responded with numerous volleys of tear gas. At least 25 officers and dozens of people were injured in the clashes, officials said. Police said at least seven people had been arrested, according to the Associated Press.
The Greek parliament is expected to vote on the deal later this week, in which Macedonia will change its name and Greece will drop its objections to the Balkan country joining NATO and the European Union.
A nationwide poll in Greece this week found that 70 percent of respondents oppose the deal, AP reported.
The agreement has caused Greek Prime Minister Alexis Tsipras to lose his four-year coalition in parliament after his nationalist allies defected to protest the deal. Following the upheaval, Tsipras narrowly won a confidence vote in parliament on Wednesday.
Tsipras has called for a televised debate on the planned name deal with Macedonia before parliament votes on the agreement.
The Greek prime minister and his Macedonian counterpart, Zoran Zaev, brokered the compromise in June to end a 27-year name dispute between the two neighbors.
Last week, Macedonia's parliament approved a constitutional revision to change the country's name. The agreement has also caused protests in Macedonia, with critics there saying the government gave up too much in the deal.
Tsipras has argued the Macedonia deal will bolster stability in Europe's Balkan region. EU countries have also strongly backed the deal.