In Ukraine uprising political groups once on the fringes are in the ascendancy: ‘We can break protesters’ legs. No one will punish us. The law is on our side’

Independence Square was a victorious arena; the hated enemy had been overthrown, his security forces driven from the streets; the capital and half the country belonged to the revolution.

The other half, however, remains loyal to Viktor Yanukovych and the reckoning which will unfold in the coming days is likely to show the alarming rise in the power of paramilitaries.

On Saturday night the prime attraction on the stage in the Maidan, as the square is known, was Yulia Tymoshenko, freed from prison and flown to Kiev to address the crowd of more than 50,000. There was heckling: it had not been forgotten that her seven-year sentence was for abusing her position as Prime Minister. There were also reminders that there had been a shift in the balance of power.

"She will not be running this country again – things have changed," said Hryhoriy Bandarenko, using an arm to clear a path; the other was entwined with that of another man who was held equally firmly on the other side. Behind them were more prisoners. They were marched through the crowd, out of the barricades, on to a minibus and driven off.

A pair of men stopped anyone from approaching the vehicle. Both were wearing body armour, helmets, blast-proof glasses, kneepads and carrying Kalashnikov AK-47s. They were taciturn, refusing to say who they were; one just muttered "security". The detained men? They had "harmed the people".

Political groups previously on the fringes are in the ascendancy. Those on the side of the opposition played a prominent part in the vicious fights with the police and are now controlling the streets of the Kiev. Those loyal to the government, who victimised protesters without fear of legal repercussions were in retreat in the capital, but have strongholds elsewhere.

The fear is that the extremists will hold increasing sway with the country in a state of political limbo. Mr Yanukovych is missing, stripped of his office by a parliamentary vote. His 140-hectare estate at Mezhyhirya, with its private zoo, collections of cars and motorbikes, dairy farm, yacht harbour and a moored galleon, was nationalised on Sunday. The new Speaker of the National Assembly and acting President, Oleksandr Turchynov, demanded that a caretaker administration be formed within 48 hours: elections are due to be held in May, but there seems to be little enthusiasm among voters for the prospective candidates.

In an address Mr Turchynov said that the country's new leadership was ready for dialogue with Russia but relations had to be on a "new, equal and good-neighbourly footing that takes into account Ukraine's European choice."

Mr Bandarenko, carrying out arrests, had described himself at a previous meeting as a member of Samooborona Maidanu (Self-Defence Forces of the Maidan). He later acknowledged that he was a member of the Right Sector, a far-right political group. It has been accused by the government of fomenting unrest, its website asking members to bring "weapons for defence" such as Molotov cocktails, at the height of the violence.

Aleksandr Muzycho, a Right Sector leader in the town of Rovno, threatened to march on the capital during the confrontation: "If those bastards [the police] won't stop, we'll take over military units, armoured personnel carriers and tanks and go to Kiev." Previously he had vowed to fight "Communists, Jews and Russians". Mr Bandarenko maintained: "that thing about the Jews was said years ago and maybe it was not rightly reported. But sure we are prepared to fight Communists and the Russians."

It was Mr Yanukovych's refusal to sign the first step of a membership process to the European Union in November which triggered the uprising. But the Right Sector, unlike many of the other protest groups, does not support joining. "We do not see why we should replace the Soviet Union with the European Union", said Mr Bandarenko. The agreement last Friday, between the government and main opposition parties, "failed because it was imposed on us by EU foreign ministers. The current political system is rotten; we shall replace it."

Right Sector's leader, Andriy Tarasenko, insisted that although the organisation is an umbrella group of nationalists such as White Hammer and Patriot of Ukraine, most of the members are ordinary people without strong political convictions who want to stand up against corruption and abuse.

Svoboda, or Freedom, party is also of the right, but is part of the political system. Its leader, Oleh Tyahnybok, who gained media prominence by being at the barricades during the strife, was suspended from Parliament after claiming there was a conspiracy by a "Muscovite-Jewish Mafia" to destabilise the Ukraine.

Mr Tyahnybok denies that he is anti-Semitic or opposed to the Russian people. Svoboda, he insists, is a serious party with 37 out of 450 deputies in parliament making significant inroads among voters in the west of the country. Its supporters have been at the forefront of the fighting.

The government, in turn, had been accused of using vigilantes, Titushkos, to attack protesters, bussing some of them in from the east to the capital. Among their victims have been AutoMaidan, an agitprop band of drivers who have blocked streets, used satellite tracking to follow police and given lifts to demonstrators. The shooting of a journalist, Vyacheslav Veremiy, has been blamed on these gangs.

According to General Viktor Palivoda, a former head of the security service: "Titushkis are actively used by the government; they are groups of provocateurs who are paid, mostly people without moral principles or very poor people who desperately need money."

The group was named after martial arts enthusiast Vadym Titushko who was filmed beating up journalists covering a pro-Yanukovych rally. But Mr Titushko has objected to the portrayal: "Titushko is a mindless, unbalanced person. No, this is wrong". He says he now supports the opposition.

The group Oplot, or "Stronghold", shares its name with the country's main battle tank, and are supporters of Mr Yanukovych's government. One posting on the website of Oplot, which describes itself as a fight club, read: "Yesterday we caught a protester and cut his ear."

Its leader, Yevhen Zhilin, declared: "I was born in the USSR and I am ready to make war for that state. Our enemies should know that before we pass them to the police, we can break off their legs, or knock out their eyes and it will be absolutely legal. Nobody can punish us for that; the law is on our side."