As demonstrators in ski masks scuffled with the police here on Tuesday evening, opposition leaders accused the government of provoking the very violence it has been condemning in an effort to discredit and possibly split the protest movement.
“We see a radicalization of the opposition. We see the escalation of the conflict, but we hear the government speak of the street,” said Irina V. Gerashchenko, a member of Parliament with the Udar Ukrainian Democratic Alliance for Reform. “This is very dangerous. The government should speak of the country, should speak of its citizens and civil society.”
Opposition leaders say the government of President Viktor F. Yanukovich has rebuffed all offers of negotiations, further fueling a dangerously volatile situation.
“Few days are left, or maybe even hours, when solving the political process is possible through negotiations,” said Arseniy Yatsenyuk, a leader of the opposition Fatherland Party. “This should be done while people are still willing to listen to politicians and accept the path to political resolution of the crisis.”
The government’s opponents pointed to three recent actions by the government that they said were intended to incite the more radical protesters and sow doubt in the minds of the moderates: new laws passed last week circumscribing the right for public assembly; the blocking of a protest march on a side street; and on Tuesday, sending cellphone messages to people standing in the vicinity of the fighting saying, “Dear subscriber, you are registered as a participant in a mass disturbance.”
Russia’s foreign minister, Sergey V. Lavrov, blamed politicians from the European Union and the United States for encouraging the fighting between the police and protesters that broke out in Kiev, the capital, over the past three days. The situation in the city, he warned, was “getting out of control.”
“It seems someone is interested in this chaos,” Mr. Lavrov said, speaking at a news conference in Moscow.
American diplomats in December had told a meeting of the Organization for Security and Cooperation in Europe that the Ukrainian government should heed the opinion of the population or risk instability, he noted. “What was this, prophesy or a prediction?”
Protest leaders said that the authorities seem to be giving the more radical protesters free rein while going out of their way to frighten more moderate sorts, particularly with the threatening text messages sent on Tuesday.
The phrasing of the message, about “participating in a mass disturbance,» echoed that in the new law making it a crime to participate in a protest deemed violent. The law took effect on Tuesday. And protesters were concerned that the government seemed to be using cutting edge technology from the advertising industry for pinpointing potential customers for political profiling.
Three cellphone companies in Ukraine — Kievstar, MTS and Life, — denied they had provided the location data to the government or sent the text messages, the Ukrainskaya Pravda newspaper reported. Kievstar suggested it was instead the work of a “pirate” cellphone tower set up in the area.
The messages appeared to have little effect. Three hours after they were sent, riot police officers pushed past barricades of burned buses at that location and were met by a crowd of protesters in ski masks and bike helmets, carrying sticks and ready to fight.
Riot police fired plastic bullets from shotguns and threw stun grenades. They pressed as far as a cobblestone-throwing catapult built by protesters the day before, and dismantled the machine before retreating again.
The opposition leaders who are members of Parliamentary factions face a difficult choice of whether to embrace or denounce the more radical groups as the demonstrations grow progressively more violent. So far, they have condemned those who are fighting with the police as not representing the aspirations of the larger number of peaceful protesters who have gathered on Independence Square since November in support of closer economic integration with the European Union.
Some of those fighting the police, carrying baseball bats and throwing Molotov cocktails say they are supporters of the European free trade agreement that began the protests.
But other groups also have appeared in Kiev, adding to the sense of chaos. Young men carrying sticks wandered side streets near the central square threatening to beat protesters who walked alone. One group shattered a shop window on the central street.
The opposition leaders have said they believe these people to be soccer hooligans and unemployed men bused into the capital by the government to provide a proxy force of street muscle to intimidate protesters and darken the image of the movement by highlighting the violence.
“Disorders should not be allowed to happen,” Vitali Klitschko, a former heavyweight boxing champion and the leader of the political party Ukrainian Democratic Alliance for Reform, wrote on his Twitter account of the thugs. “This is a plan of authorities to introduce a state of emergency.”
Early Tuesday morning, opposition activists detained a dozen or so of these rival young men and marched them back to one of several buildings occupied by protesters, where several admitted in videotaped conversations that they had been promised 200 hryvnia, or about $25, to cause trouble, but were not able to explain clearly who had hired them.
A civic activist who has been prominent in the movement, Ihor Lutsenko, was missing on Tuesday after unknown men forced him into a car in the parking lot of a hospital, according to a Facebook post by Mr. Lutsenko’s wife.
The protests that peaked in December had seemed to be fading but were re-energized by opposition to the new laws against public assembly passed last week.