A group of young masked demonstrators attacked a cordon of police with sticks, burned police buses, and pushed through, to the parliament building after opposition politicians called on people to disregard the new legislation.
The small win for protesters might be short-lived as reports suggest that further reinforcements of riot police are surrounding the whole of downtown Kyiv.
"Whatever they are trying to do, these radical branches, it’s important to note that they don’t have the backing of the rest of the movement," freelance reporter Gulliver Cragg told CBC News from Independence Square in the capital.
It is not known whether the police gathering on the fringes of the protests are going to act or if they are there as a back-up plan.
"Everyone is wondering whether they will try to do this tonight — using of course those new laws that were passed that gives them fully the right to do so with impunity for any violence that they may use in the process," said Cragg.
Despite appeals from opposition leaders not to resort to violence, and a personal intervention from boxer-turned-politician Vitaly Klitschko, protesters continued to throw smoke bombs and hurl fireworks and other objects at police.
The interior ministry said 70 police were hurt, more than 10 committed for hospital treatment and four in serious condition, according to Cragg. It is not known how many protesters have been injured in the fracas.
A spokeswoman for Klitschko tweeted that President Viktor Yanukovich had agreed to meet Klitschko immediately at the presidential residence outside Kiev, although there was no confirmation from Yanukovich's side.
Police have used water cannons against demonstrators gathered near the parliament building and the heavily protected government headquarters, eyewitnesses said.
Up to 100,000 Ukrainians massed on Kyiv's Independence Square in defiance of the sweeping new laws, which ban rallies and which Washington and other Western capitals have denounced as undemocratic.
The rally, the biggest of the new year, was the latest in a cycle of public protests in the former Soviet republic since Yanukovych made a policy U-turn in November away from the European Union towards Russia, Ukraine's former Soviet overlord.
Ukrainians have been pushing for closer ties with the European Union and loosening ties with Russia. The new series of laws passed by the government on Thursday — which protesters are calling "Black Thursday" — caused controversy as some have viewed the process as "fast and loose" and "unconstitutional."
"The laws were passed by a show of hands. They didn't even actually properly count the votes. It was from a later scene in photographic evidence that they saw they didn't have the majority that the speaker of parliament said they had," said Cragg.
The court ban on protests published on Jan. 15, and last Thursday's legislation aimed at prohibiting all form of public protests, have inflamed tensions again.
The laws - denounced by the United States and other Western governments as anti-democratic - ban any unauthorized installation of tents, stages or use of loud-speakers in public.
"Yanukovych and his henchmen want to steal our country. Ukraine is united as never before in its struggle against those in power today, in its determination not to allow a dictatorship," Klitschko, the strongest potential challenger for the presidency, told the crowds on Independence Square.
Several big protests in December attracted hundreds of thousands of people, while thousands maintained a vigil in a Kyiv square demanding Yanukovych resign. Since the new year demonstrations have become smaller, but hundreds of people are still camping in the square and 50,000 turned out a week ago.
"They see this as a movement to defend democracy in Ukraine more than anything else," said Cragg.
Heavy jail sentences were imposed for participation in "mass disorder" and the wearing of face-masks or protective helmets. Dissemination of "extremist" or libellous information about the country's leaders was outlawed.
In a gesture of scorn for the helmet ban, many protesters on Sunday wore saucepans and colanders on their heads.
The crisis has highlighted a divide in the country of 46 million people between those, particularly in Russian-speaking eastern areas, who identify more closely with a shared past with Russia and those, especially in the Ukrainian-speaking parts of western and central Ukraine, who look westwards.
Opposition leaders announced an action plan to gather people's signatures expressing no confidence in the leadership of Yanukovych and parliament.
Opposition urges for calm
When clashes broke out about 500 metres from Independence square, Klitschko went to the scene and sought to persuade protesters to refrain from attacking police.
"Stop your actions," he called through loud-hailer to groups of young people - some of them masked. "We are a peaceful protest." Protesters sprayed a powder fire extinguisher at police, catching Klitschko whose face was covered in white.
Arseny Yatsenyuk, another opposition leader, told the crowds on Independence Square: "Our victory is not in using physical violence but in moral and spiritual strength."
Though setting up an alternative power structure may not be realistic, Sunday's turn-out suggested it could also be difficult for the authorities to try to solve the crisis by use of force despite the court ban and the new laws.
Russia has since thrown Ukraine a $15 billion lifeline in credits as well as a softer deal for purchases of strategic supplies of natural gas.