Pro-Russian separatists who seized a provincial building in the eastern Ukrainian city of Donetsk have reportedly declared an independent "people's republic" in a move that echoes events leading to last month's secession of Crimea.
You can see video of the scuffle between police and protesters that led up to the storming of the building here.
After the takeover of the building, one Russian speaker appeared at a podium, proclaiming "the creation of the sovereign state of the People's Republic of Donetsk," according to Al-Jazeera. The Associated Press reports that afterward "a barricade of car tires and razor wire" was erected outside the building to keep police from retaking it.
Ukrainian police responded by closing all roads leading into the city.
"Unknown people who are in the building have broken into the building's arsenal and have seized weapons," police said in a statement on Monday.
"The rebels have called for a referendum on secession from Ukraine by 11 May.
"Ukrainian security officials are being sent to the eastern cities of Donetsk, Luhansk and Kharkiv after pro-Russia groups occupied government buildings.
"Interim President Oleksandr Turchynov called the unrest an attempt by Russia to 'dismember' Ukraine.
"In an address on national TV, he said it was 'the second wave' of a Russian operation to destabilise Ukraine, overthrow the government and disrupt planned elections."
On Sunday, pro-Russian mobs also stormed buildings in Luhansk and Kharkiv, two other cities in the country's east that have large numbers of Russian speakers and strong pro-Moscow sentiment.
NPR's Ari Shapiro, reporting from Kiev, says Ukraine's acting Prime Minister Arseniy Yatsenyuk has accused Russia of instigating protests as a pretext to invade eastern Ukraine.
"It is a plan to destabilize the situation, a plan to let the foreign military forces cross the border and occupy the country, which we are not going to tolerate," Yatsenyuk said.
Russia has argued that Ukraine's regions should have more autonomy. The ominous developments also come as the Kremlin has reportedly massed thousands of troops on the border with Ukraine.