Ukrainian authorities on Tuesday reasserted control over an administration building in Kharkiv, the country's second-largest city, evicting pro-Russian protesters and detaining dozens.
In Donetsk, a city 250 kilometers (155 miles) further south, the makings of an improvised self-appointed government began taking shape as demonstrators dug in for their third day at the 11-story regional administration headquarters.
Serhiy Taruta, the officially appointed Donetsk governor, scoffed at events in the city.
''I call this a theater of the absurd,'' he said. ''It is just artists performing, but the main thing is that there is an ever-dwindling audience.''
Both cities are in Ukraine's east, where hostility is strong toward the government that took power in February after the ouster of Kremlin-friendly President Viktor Yanukovych.
Even though Ukraine's interim authorities have achieved some success in quelling unrest that swept across eastern provinces Sunday, festering discontent threatens to undermine plans to hold a presidential election on May 25.
Addressing parliament, acting President Oleksandr Turchynov said security forces retook control of the Kharkiv administration building early Tuesday. He said that several police were injured in the clashes with the separatists.
Interior Minister Arsen Avakov described the measure on his Facebook page as an ''anti-terrorist operation.''
In a session briefly interrupted by a brawl, Parliament also voted to toughen punishment for undermining Ukraine's national security, imposing jail terms of up to 5 years for separatism.
In Donetsk, there was little sign Tuesday afternoon that government forces had any immediate plan to clear the regional administration building.
The city has seen weekly rallies typically culminating in a march on local government offices, but Sunday saw an escalation of that strategy when groups of masked men carrying batons burst through police lines to take over the building.
By Tuesday, lines of car tires wrapped in razor wire had been erected as deterrent against a possible attempt by police to storm the premises. The tactic appears to have been copied from the anti-government protests in the capital, Kiev, which led to Yanukovych's overthrow, when demonstrators set alight tires in order to keep riot police from advancing.
Just like it was in Kiev, feeding stations have been created inside the administration building, supplied by volunteers and local residents.
No clear leader or agenda has emerged from the obscure group of pro-Donetsk autonomy activists behind the standoff.
A declaration adopted Monday claimed sovereignty for what autonomy activists have dubbed the Donetsk Republic and called for a referendum on the issue to be held no later than May 11. While none of the self-appointed leading figures in the Donetsk Republic movement has said they necessarily want the region to join Russia, they have also declined to rule out the option.
Despite claims by the autonomy groups to represent the entirety of Donetsk, a region of more than 4 million people, rallies outside the regional administration building have since the weekend drawn crowds only in the low thousands.
In a third eastern city, Luhansk, pro-Russia groups remained in control of the local branch of the security services, which they seized over the weekend. There have been no attempts to recapture the building.
The Luhansk police chief called on protesters to surrender their guns and said parliament was considering an amnesty that would be extended to them.
The seizures of the buildings and calls for referenda were an echo of the events that led to Russia's annexation of Ukraine's Crimean peninsula last month. After Yanukovych fled to Russia, Russian troops took control over Crimea and the region voted to join Russia in a hastily called referendum.
The West has not recognized the vote or the annexation and has retaliated with sanctions against Russia.
Even as the United States warned Russia of further sanctions if Moscow takes further efforts to destabilize Ukraine, the White House announced Tuesday a high-level meeting among U.S., EU, Ukrainian and Russian diplomats in the coming days to try to solve the crisis.
Russia's Foreign Minister Sergey Lavrov said in Moscow on Tuesday that the date and format of the four-way talks haven't yet been agreed. He suggested that Ukraine's presidential candidates could be invited to join the negotiations and emphasized the need for the regions to take part in drafting Ukraine's constitutional reform.
The Kremlin has pushed for a constitutional reform in Ukraine that would turn it into a federation with broad powers for its regions and ensure the country's neutrality - demands that reflected Russia's desire to maintain influence over its neighbor and prevent it from joining NATO.