MPs in Greece are preparing to ratify a historic pact that will allow Macedonia, the country’s northern neighbour, to change its name.

The accord has sparked mass protests on the eve of the vote to resolve one of the world’s most abstruse diplomatic rows.

While a vote in favour of the Prespa agreement on Friday afternoon is considered highly likely, the atmosphere both in and outside Athens’s parliament was tense on Thursday evening. Demonstrators railed against an accord described as a national sellout by opponents demanding a referendum. Officers fired tear gas to disperse crowds as protesters waved Greek flags and chanted “Hands off, Macedonia”. A small number of people launched Molotov cocktails, rocks and flares.

Under the agreement, the former Yugoslav republic will be renamed North Macedonia, paving the way to membership of Nato and ending a dispute that has divided the two Balkan nations for decades. But the backlash is fierce.

“This treason has to stop,” said Dimitris Orfanoudakis, a farmer who travelled to the capital from Crete to shout himself hoarse at the demonstration with his teenage son, Giorgos, draped in a blue and white Greek flag. “We are the only people in the world who have to defend our borders from our own politicians because what they are doing is a national crime. Macedonia is one, and it is Greek.”

Dimitris Orfanoudakis and his son, Giorgos, travelled from Crete to protest against the pact. Photograph: Helena Smith/The Guardian

Indicative of the mood ahead of Friday’s ballot, more than 1,500 police threw a security cordon around central Athens as black-clad youths chanted “traitors” at lawmakers.

“We feel betrayed,” Zografos Stathakopoulos, a 47-year-old protester, said on Thursday. “Most Greeks don’t want this deal, but politicians are betraying us.”

Police said they arrested 10 people and detained another 133 on suspicion of committing or planning acts of violence before the protest broke up. A new demonstration has been called outside parliament for Friday.

The government had originally called the vote for Thursday night but was forced to delay it after parliamentarians across the board demanded to address the chamber as four days of stormy debate climaxed over the issue.

“You have surrendered the monopoly of the name Macedonia,” fumed the socialist party leader Fofi Gennimata giving voice to long-held Greek fears of irredentist claims over the country’s own province of Macedonia. “You have given up Greece’s geostrategic position.”

Earlier in the day the KKE communist party, which had also called on followers to protest against the landmark name-change deal, unfurled a giant banner across the great walls of the ancient Acropolis deploring it as a plot of the “US, Nato and the EU”. A similar rally that drew tens of thousands on Sunday turned violent when rock and crowbar-wielding protestors attempted to storm parliament, prompting police to respond by firing copious rounds of teargas.

Since the dissolution of Yugoslavia, Greece has argued that use of the name Macedonia would unleash territorial ambitions over its own province of the same name in a part of the world where borders are prone to shifting. Concerns had been fuelled by the landlocked republic appropriating figures and symbols from ancient Greek history including the erection of a gargantuan statue with an uncanny likeness to Alexander the Great – the most famous Macedonian of all – in Skopje’s central square.

For Greece’s leftist prime minister, Alexis Tsipras, and his Macedonian counterpart, Zoran Zaev, adding the geographical qualifier of “north” to the state’s new name was an honourable compromise that, once accepted, could normalise ties in the otherwise volatile western Balkans. Greece had vetoed the state’s membership of both Nato and the EU since 2008 because of the name row.

Friday’s vote followed a similar endorsement of the accord by the Skopje parliament earlier this month. Under the treaty, Athens also has to vote for the pact before it can pass into law.

Internationally, both leaders have been praised for the courage they have displayed defying nationalist sentiment on the ground. But what European officials see as “a unique and historic opportunity” to settle a dispute that has defied a solution for decades has tested the two politicians at home.

“Tsipras submitted to pressure from the Europeans, especially [Angela] Merkel,” said Panos Kammenos, who heads the populist rightwing Independent Greeks party, the ruling leftists’ junior partner in government until it pulled out in protest over the accord.

In northern Greece, which abuts the ex republic and bears the same name, nationalist fervour was at a high pitch on Thursday, with hundreds of farmers and local residents blocking the main border crossing between the two states.

MPs from the region who signalled they will vote in favour of the accord have received death threats. Late on Wednesday arsonists set fire to the home of a female lawmaker representing Tsipras’s Syriza party in the northern town of Yiannitsa. Many deputies have confessed privately to being in fear of confronting constituents.

Successive surveys show around 70% of Greeks are opposed to the agreement. “Greeks have vivid memories of Macedonia being fought over four times in the past century alone,” said Angelos Syrigos, professor of law and foreign policy at Athens’ Panteion University. “This agreement would have been a fair compromise if the new name applied to everything and by that I mean language, citizenship and nationality. Right now we have something in between. If our neighbours are known as ‘Macedonians’ who speak the ‘Macedonian’ language that in the future could be the basis for territorial claims.”

Tsipras’s minority administration, which controls 145 MPs in the 300-seat house following Kammenos’s departure, needs the support of six opposition deputies to pass the draft bill into law and with the backing of centrists and Independent Greek party defectors is expected to win the vote.

But the response could be combustible and unexpected in a country that that has become increasingly polarised as general elections loom. “We will take to the streets as they have done in France,” said Orfanoudakis, the Cretan farmer. “There’s going to be chaos. After eight years of financial crisis, of having foreigners pauperise us, they are not going to take our Macedonia away too.”