Russian forces invaded Ukraine on Thursday, staging an assault by land, sea and air in the biggest attack by one state against another in Europe since World War II.

Speaking in a televised address on Thursday, Draghi said it was impossible to have meaningful dialogue with Moscow and demanded that Russia unconditionally pull its forces back to the internationally established borders.

“We have our allies at our side ... together we will do whatever it takes to preserve Ukraine’s sovereignty, Europe’s security, and the integrity of the international order based on the rules and values we all share,” he said.

His comment echoed a famous pledge that he made in 2012, when he was president of the European Central Bank, to do “whatever it takes” to save the euro.

Draghi offered the “full and unconditional solidarity” of Italy towards Ukraine and said the Italian embassy would remain open and fully operational in Kyiv.

“What is happening in Ukraine concerns all of us, our existence as free people, our democracy,” he said, adding that European Union leaders would impose a “very tough package of sanctions” on Russia later in the day.

“We have made it clear in every forum that we are ready to impose severe consequences ... Now is the time to apply them.” 

French President Emmanuel Macron concurred, adding that Russia could expect tough sanctions that would hit its military, its economy and its energy sector.

“The events of last night mark a turning point in the history of Europe,” Macron said in a televised address to the French nation, standing before French, European Union and Ukrainian flags.

“We will respond to this act of war without weakness, with cold blood, determination and unity,” he added.

French Foreign Minister Jean-Yves Le Drian had also earlier said that France would reinforce its support to Ukraine “in all its forms”, without further specifying whether or not this could include military means.

British Prime Minister Boris Johnson, speaking shortly before Macron in a televised address from Downing Street, had also said that Britain and its allies would unleash a massive package of economic sanctions to hobble the Russian economy.

“I don’t believe that the Russian dictator will ever subdue the national feeling of the Ukrainians and their passionate belief that their country should be free,” he said.

Western leaders were due to discuss further steps during several high-level formats on Thursday, including an emergency NATO meeting.

- With AAP