Russian President Vladimir Putin has authorised military operations across eastern Ukraine ahead of what some fear will be a full-scale invasion.
Ukraine has declared a 30-day state of emergency following reports of a Russian military assault in the nation’s east.
Moments after President Vladimir Putin’s television address on Russian state TV, shelling was heard from the Ukrainian capital of Kyiv, with reports of an attack on a number of regions, including the city of Donetsk.
President Putin has described the attack as a “special military operation”, claiming the assault is a response to the Ukrainian government’s efforts to build ties with NATO.
“All responsibility for bloodshed will be on the conscience of the ruling regime in Ukraine," President Putin said.
According to Ukrainian President Volodymyr Zelenskyy, Moscow had turned down an invitation for talks.
"Today I initiated a telephone conversation with the President of the Russian Federation. The result was silence," he said.
US President Joe Biden has condemned the “unprovoked and unjustified” attack.
"President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering,” he said on Twitter.
“Russia alone is responsible for the death and destruction this attack will bring, and the United States and its allies and partners will respond in a united and decisive way.
Subscribe to the Defence Connect daily newsletter.
Be the first to hear the latest developments in the defence industry.
“The world will hold Russia accountable."
President Biden has committed to imposing further sanctions on Russia, in addition to financial restrictions introduced earlier this week.
Following an emergency meeting in New York, UN Secretary General Antonio Guterres has called on Russia to withdraw its forces.
"President Putin, in the name of humanity, bring your troops back to Russia," he said.
Ukraine has restricted civilian flights in its airspace due to "potential hazard", with Russia also partially closing its airspace in the Rostov flight information region to the east of its border with Ukraine.
The attack comes just a day after President Putin recognised two separatist regions as independent and ordered the deployment of what he described as “peacekeeping” troops.