The interim government in Kyiv threatened to use force by early Monday to remove pro-Russian forces from government buildings in eastern Ukraine. The deadline passed without any action from the Ukrainian forces, but separatists didn’t just sit on their hands. Demonstrators seized a police building in another city near the Ukraine-Russian border this morning:

Pro-Russian separatists on Monday seized a police building in yet another city in Russian-leaning eastern Ukraine, defying government warnings that it was preparing to act against the insurgents.

Dozens of angry men hurled rocks, smashed the windows and broke into a police station in the city of Horlivka not far from the border with Russia, while hundreds of onlookers cheered them on. Thick white smoke rose from the entrance to the building.

The events in Horlivka were the latest sign of trouble in Russian-speaking eastern and southern regions, in which pro-Russian gunmen have seized a number of government buildings demanding more autonomy from the central government and closer ties with Russia.

So far, Kyiv has not yet sent its forces into action after the expiration of its deadline. Or have they?

Acting President Oleksandr Turchynov issued a decree Sunday that those protesters who disarm and vacate government offices in several cities in the Russian-leaning east of the country by 0600 GMT Monday will not be prosecuted. Turchynov vowed that a “large-scale anti-terrorist operation” would take place to re-establish control over those areas and that the fate of the Crimean Peninsula, annexed by Russia last month, will not be repeated.

There was no immediate comment from the government on the deadline passing.

But Serhiy Taruta, governor of the Donetsk region, where government buildings in several cities, including the regional capital Donetsk, have been seized by pro-Russian gunmen, said an anti-terrorist operation was underway in the region, according to the Interfax news agency.

Taruta did not give any details of what the anti-terrorist operation would entail. The governor usually does not have authority to launch anti-terrorist measures on his own and he was likely acting on the orders of top security officials in Kiev.

CNN’s Nick Paton Walsh says that only one brief, early clash took place, and that Horlivka has all but fallen — and CNN has some dramatic video of the seizure of the government building:

Ukrainian officials have placed blame for unrest in the eastern section of their country squarely on their neighbor. The new Ukrainian government said the security operations were launched against terrorists who are attempting to “destroy our country.”

Giving no further details, it also said it had “concrete evidence of Russian special service involvement” in the pro-Russian protests and storming of buildings and would present it at an international meeting on the Ukraine crisis on Thursday.

Ukrainian security forces launched an operation Sunday to clear pro-Russian separatists from a police headquarters in the eastern city of Slaviansk, officials said.

However, a CNN crew in the city saw no sign of a large presence of Ukrainian security forces — with the exception of a single police car and a helicopter flying above — nor any confrontation with the occupiers.

Gunmen dressed in camouflage had stormed and seized the police building a day earlier in Slaviansk, a town about 100 miles from the Russian border, and set up barricades around it.

The hesitation comes, no doubt, from worries that any kind of military force used could trigger an invasion by Russia:

But NPR’s Ari Shapiro, who is in the eastern Ukrainian city of Donetsk, reminds our Newscast Desk that Ukraine’s government has promised it will use force, if necessary, in a bid to regain control. With up to 12,000 Ukrainian troops reportedly poised to enter the region, “people here are afraid of all-out war,” Ari says.

There are also fears, of course, about what might happen after any such action by Ukrainian forces. The AP notes that “Russia has warned the Kiev government against using force against the protesters in the east and has threatened to cancel international diplomatic conference on the Ukrainian conflict scheduled for later this week.”

Last month, Russian forces moved into what was the Ukrainian-controlled Crimean peninsula. Since then, Russia has annexed Crimea — an act that Ukraine, the U.S. and many other nations have deemed a violation of international law.

Last night, the UN Security Council held an emergency session about the situation in Ukraine — at the request of Russia. The Russian ambassador tried to claim that “anti-Semitic” forces were attempting to seize power, but the meeting became an opportunity to castigate the Russians instead. US Ambassador Samantha Power flat-out accused Russia of fomenting unrest as a pretext for further land grabs, and pledged more aid to Ukraine:

The Russian gambit seems to be working well enough. I wonder what Vladimir Putin thought he’d gain from calling the UNSC meeting. Perhaps he thought Russia could pre-empt action by demanding it himself, but it’s a rare miscalculation — instead setting Russia up for a public whipping. It’s doubtful that this will deflect Russia from its overall course, but it’s a public-relations smackdown they didn’t need.