On Thursday, Ukrainian President Volodymyr Zelensky accused Russia of building up troop presence on the border and the United States pledged to stand by Ukraine in the event of Russian intimidation.

“There is no doubt such a move would lead to a further increase in tensions close to Russia's borders. Certainly, this would call for additional measures from the Russian side to ensure its security. Russia is not threatening anyone, it has never threatened anyone,” Kremlin spokesman Dmitry Peskov told reporters.

The war in eastern Ukraine broke out when the Crimean Peninsula, north of the Black Sea in Eastern Europe, was annexed by the Russian Federation between February and March 2014.

Since then, the peninsula has been administered as two Russian federal subjects—the Republic of Crimea and the federal city of Sevastopol.

The annexation from Ukraine followed a Russian military intervention in Crimea that took place in the aftermath of the 2014 Ukrainian revolution and was part of wider unrest across southern and eastern Ukraine.