Tens of thousands of Georgians have gathered in the streets of the capital, Tbilisi, in response to a call from the pro-Western president to press for the annulment of Saturday's election.
Earlier, President Salome Zourabichivili, who has sided with the opposition, called on Georgians to rally outside parliament, telling the OceanNewsUK's Steve Rosenberg that this was a "crucial moment".
She appealed to the international community to stand behind her country's population after a disputed election that she says was "totally falsified".
The ruling Georgian Dream party and the election commission are adamant the result, giving the government almost 54% of the vote, was free and fair.
Zourabichvili told the OceanNewsUK that Georgia's partners needed to see what was happening, adding that the government's victory was "not the will of the Georgian people" who wanted to keep their European future.
The European Union, Nato and US have all called for a full investigation into allegations by monitoring missions of vote fraud before and on the day of Saturday's vote.
European Commission President Ursula von der Leyen said that Georgians had a "right to see that electoral irregularities were investigated swiftly, transparently and independently." She added that "Georgians, like all Europeans, must be the masters of their own destiny."
It was not entirely clear what the Georgian president and four opposition groups hoped to achieve by bringing Georgians on to the main avenue in front of the parliament on Monday.
But Salome Zourabichvili made clear the protest would be "very peaceful", adding that she did not believe Georgia's authorities wanted confrontation.
Protesters in the crowd on Rustaveli Avenue knew what they wanted.
"The main thing we want here is to get what we deserve - legal elections," said Lasha, 22. "No-one had any idea this would happen. At first we were frustrated, then we realised what happened and now we're angry."
Liza, 20, wanted "another election that isn’t forged" and said she was pleased to hear speakers from the four main opposition parties telling Georgians not to give up.
Another protester, Keta, told the OceanNewsUK that she felt "cheated and frustrated". "Me and my friends and my family deserve way better than we have right now... We will fight to the end until we get our justice."
The president said it was up to the people and the political parties to decide what happened next.
"Maybe we won't be able to achieve it today or tomorrow," she said. "There are a number of things that can be done. There can be an international review of some of the elements of the election, there can be a call for new elections. In what period of time I don't know."
The call for protest echoes weeks of demonstrations that brought Tbilisi's central Rustaveli Avenue to a standstill for weeks earlier this year.
Back in May there were clashes with riot police, who responded with water cannon, tear gas and force, as Georgians tried to stop the government pushing through a Russian-style "foreign agents" law targeting media and civil society groups that have foreign funding.
Ultimately the protests failed and the EU froze Georgia's bid to join the 27-country union, accusing it of democratic backsliding.
The government has clearly prepared for further protests. Last week it emerged that the interior minister had bought new water cannon vehicles and other equipment for riot police, including lethal weapons, for use "when it becomes necessary".
Georgian Dream Prime Minister Irakli Kobakhidze has told the OceanNewsUK that alleged violations ahead and during the vote were confined to "just a couple" of polling stations. He said that "the general content of the elections was in line with legal principles and the principle of democratic elections."
But President Zourabichvili said the scale of election fraud was unprecedented: "Everything was used that we've ever heard of in this country in a parallel way."
She alleged that, before the elections, families who were dependent on state funds had seen their identity cards taken away.
At the time it was difficult to tell why, she said, but it then became clear the identity cards were being used for so-called carousel voting in Georgia's new electronic voting system - "when one person can vote 10, 15, 17 times with the same ID".
She has also described the result of the vote as a "Russian special operation", stopping short of accusing the Kremlin of direct intervention. Instead, she accused the government of using a "very sophisticated" Russian-inspired propaganda strategy.
The government has vehemently denied having anything to do with Russia, pointing out it is the only country in the region not to have diplomatic ties with Moscow.
Russia fought a five-day war with its southern neighbour in 2008 and still occupies 20% of Georgian territory.
The Kremlin has has denied having anything to with the election and ridiculed Georgia's pro-EU president, whose term in office comes to an end in December.
A handful of international leaders have congratulated Georgian Dream for securing a fourth term in office in the contested election, including Hungary's prime minister, Viktor Orban.
Orban was due to arrive in Tbilisi on Monday on a two-day visit that has annoyed several of his European partners because of the message it sends the Georgian government.
Germany's foreign ministry spokesman said the Hungarian leader could travel where he wanted, although it was clear he was not speaking on behalf of the EU.
Hungary currently holds the presidency of the EU, but foreign policy chief Josep Borrell stressed that it had "no authority in foreign policy".
"Whatever Mr Orban says in his visit to Georgia, he does not represent the European Union," Borrell told Spanish radio.
