Groups of hardcore football fans from across Ukraine have emerged as a driving force in the protests against President Viktor Yanukovych, adding to the pressure on him even in his eastern strongholds.
Football "ultras" from the pro-EU west of the country have played a leading role as the protests have grown more radical over the last two weeks, helping seize local government buildings in cities such as Lviv.
In Kiev, ultras from the capital's best side, Dynamo Kiev, have been at the frontline of clashes with security forces that took place at the gates of their own stadium.
But they have also turned against Yanukovych in the Russian-speaking east of the country. Even fans of his native city's Shakhtar Donetsk have joined the protest, along with Metalist and Dnipro fans in the eastern cities of Kharkiv and Dnipropetrovsk.
"Thank you, fans of Shakhtar, Metalist, Dnipro, who performed together with the Ukrainian people," influential opposition figure Petro Poroshenko said hours after Yanukovych's first concessions to the opposition.
"Let's applaud to the heroic football fans. That's true solidarity!" said nationalist leader Oleg Tyagnybok.
The involvement of football fans from the east was unexpected, given that the owners of the clubs are oligarchs close to the authorities.
"Fans of Shakhtar personally decided to protect the people who came to express their dissatisfaction with the authorities and lawlessness," ultras from the Donetsk club said in a statement.
By far Ukraine's strongest club, and possibly the only world-class side in the ex-USSR, Shakhtar belongs to Ukraine's richest man and the main sponsor of the ruling party, Rinat Akhmetov, who earlier strongly opposed the use of force against protesters.
"We came to support our people in fighting for their rights. We are against the regime," said the ultras.
A YouTube video showed about 60 Shakhtar fans gather last week in central Donetsk, their faces covered with masks or scarves.
They surrounded the activists in a bid to protect them from attacks by police or government supporters.
"Any attack on us... threatens our lives, our rights. Glory to Ukraine! Glory to the heroes!" they chanted, using a Ukrainian nationalist slogan usually taboo in the east.
'The government got on our nerves'
The list of towns whose fans who have supported the protests centred on Independence Square in Kiev -- known as the Maidan -- now extends across Ukraine.
"Ultras decided to support the Maidan as it fights for justice, for freedom. Those values are close to the fans," Igor, an ultra fan for Dynamo Kiev, told AFP.
"It is common for football fans to have a heightened sense of justice," he said. "The government got on our nerves with all its impudence, ruthlessness, and impunity."
He said Dynamo Kiev's fans were not only fighting on the barricades, but also working to protect the tent city on the Maidan.
Some distribute promotional material and others take part in the protests as ordinary citizens.
Some protesters in Kiev can also be seen wearing the unmistakable green and white colours of Karpaty Lviv from western Ukraine.
Their team famously won the Soviet cup in 1969, but not a single major trophy since -- yet it still inspires a fanatical following.
Some Metalist fans from Kharkiv near the border with Russia also decided to "protect" pro-European protesters from attacks by aggressive pro-government activists.
Without using symbols of the club, Kharkiv ultras took to the streets together with Dynamo Kiev fans, usually seen as their enemies.
Sergiy Kurchenko, the young businessman who owns FC Metalist -- and who is close to the presidential clan -- urged fans not to use symbols of the club outside football, threatening to restrict access to matches.
Earlier, the Kiev fan movement Ultras Dynamo announced the creation of vigilante groups to protect Kiev residents from so-called "Titushkos" -- pro-regime thugs who attack activists and reporters.
"The protest is directed against the current government which caused a rebellion of the whole society," said Kiev fan Igor.