Russia’s military said Wednesday that its troops had closed the border with Belarus in response to what it called an incursion by Ukrainian forces into the country’s far north.
The move came hours after Russian President Vladimir Putin said that Russia would respond with force if Kiev did not agree to a cease-fire.
“In response to a recent incursion of Ukrainian forces in the region of Omsk, the Armed Forces of Russia and the Russian Federation will close the airspace and the borders of the Russian territory of the Far North,” Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov told reporters.
He did not give further details.
The incursion into Omsky has been a cause of great concern in the country, which has been under a state of emergency since the Euromaidan protests that began in 2014.
On Monday, Ukrainian troops opened fire on Russian troops near the Ukrainian-Russian border and in Odessa, killing at least nine Russian servicemen and wounding more than 100 others.
The Russian Foreign Ministry called the attack a “flagrant provocation.”
Ukrainian President Petro Poroshenko on Tuesday urged Russia to halt its incursions into the border region and said that if Moscow continued to attack, Ukraine would be ready to respond militarily.
The Ukrainian military on Tuesday said its forces had been sent to a nearby border town of Mariupol, near the Russian border.
Ukraine has imposed a state emergency in the area in the wake of the Odessa protests, which led to the ouster of the government in Ukraine’s east.
Ukraine’s government is trying to hold off Russian forces and a pro-Russian separatist leader in the Donetsk region, who has been fighting with Ukrainian forces for more than two years.
The conflict has prompted an exodus of hundreds of thousands of civilians and thousands of troops, many of whom have been fighting for control of the Ukrainian border and the region’s strategically important port of Mariapol.
On Wednesday, the Ukrainian army said that Russian forces had crossed the border into the Mariupols region and killed at least three Ukrainian servicemen.
A statement from the military’s chief of staff, Gen. Alexander Zakharchenko, said the Ukrainian forces were attempting to breach Ukrainian territory but that they were “not able to penetrate the Ukrainian territory and were confronted by Russian forces.”
The statement did not provide further details on the Russian involvement.
Ukraine and the West have blamed Russia for a series of deadly attacks in the past year against civilians in the east of the country.
Moscow denies any involvement in the attacks, and the government has accused the West of supporting Kiev’s armed rebellion.
The Ukraine government says more than 10,000 people have died since April 2016 in clashes between pro- and anti-government forces, which left at least 4,000 dead.
On Tuesday, Ukrainian forces said they had regained control of a major road connecting the Russian-occupied town of Ilovaisk and Mariupole, which was surrounded by Russian troops and rebels on Tuesday.
The town’s population had fled amid the fighting, and authorities said that there were no casualties among the evacuees.