UK Edition
Vladimir Putin officially declared a military offensive on Ukraine in the early hours of Thursday morning, followed minutes later by explosions in the capital of Kyiv and across the country.
In an angry address broadcast just before 6am Moscow time, the Russian president said he could not tolerate what he called the threats from Ukraine.
"I have made the decision of a military operation," he said in the televised speech.
Following the end of his short speech, which coincided with an emergency meeting of the United Nations Security Council, explosions were reported in Kyiv, Odessa, Ukraine’s third-largest city, as well as the city of Kramatorsk in the eastern Donetsk region.
Terrified citizens across the country rushed to bomb shelters as dawn broke, while air raids warnings sounded in the capital.
Russia's defence ministry claimed it was using "high-precision weaponry to take out Ukrainian military infrastructure, air defence, aerodromes, and aviation." Ukraine's Interior Ministry, meanwhile, told CNN there have already been casualties.
Broadcasting live from his phone, President Volodymyr Zelensky said he would declare nationwide martial law and urged Ukrainians to stay home.
"Don't panic. We are strong," he said, following a phone call with US President Joe Biden. "We are ready for everything. We will defeat everyone. Because we are Ukraine.”
Mr Biden reacted immediately to reports, calling Mr Putin’s offensive “unprovoked and unjustified”.
“President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering,” he warned, promising the US and its allies will respond in a “united and decisive way”.
Mr Biden is due to meet virtually with G7 leaders at 9am ET.
The US and European partners are reportedly planning on Thursday to trigger the “full scale” of the sanctions that have been discussed over the course of the last several weeks.
A US official told reporters Ukraine was witnessing “pre-assault fires”.
“Expect this to go on for a few hours,” they said. “Then an attack will follow with all of the full forces Putin has arrayed. It’s begun.”
Dmytro Kuleba, Ukraine's Foreign Minister, tweeted: "Putin has just launched a full-scale invasion of Ukraine. Peaceful Ukrainian cities are under strikes.
"This is a war of aggression. Ukraine will defend itself and will win. The world can and must stop Putin. The time to act is now."
Putin warns of 'consequences they have never seen'
Mr Putin claimed that Russia’s goal was not to occupy Ukraine, but merely protect residents of eastern Ukraine from what he called a “regime”.
He said the goal of the attack, for which he has positioned 190,000 Russian soldiers along Ukraine’s border, was the “demilitarisation and de-Nazification of Ukraine".
"We will bring to court those who have committed many crimes, responsible for the bloodshed of civilians, including Russian citizens," he said.
Mr Putin urged Ukrainian soldiers to put down their weapons and go home, saying they would be responsible for bloodshed if they did not.
He warned other countries that any attempt to interfere with the Russian action will lead to "consequences they have never seen".
Earlier in the evening, civilian aircraft were warned away and the airspace above Ukraine was largely clear.
Mr Biden said on Thursday he will “speak to the American people to announce the further consequences the US and our Allies and partners will impose on Russia for this needless act of aggression against Ukraine and global peace and security”.
'Send your troops and your tanks and your planes back'
As Mr Putin spoke, the UN Security Council met to discuss developments on Wednesday night, in the 15-member body's second late-night meeting on the crisis this week.
In surreal scenes, Ukrainian and Russian representatives exchanged fire in New York.
"You declared war!" Sergiy Kyslytsya, Ukraine's ambassador to Russia, told the council.
"Should I play the video with your president declaring war?"
Vasily Nebenzya, Russia's ambassador, retorted: "This is not called a war, this is called 'a special military operation' in (the breakaway region) Donbas."
A draft resolution calling out Moscow over its actions towards its neighbour is doomed to fail due to Russia veto power.
"President Putin, stop your troops from attacking Ukraine, give peace a chance, too many people have already died," Antonio Guterres, UN Secretary-General, said, issuing a personal plea.
Linda Thomas-Greenfield, US Ambassador to the UN, urged the Russian president: "Send your troops and your tanks and your planes back to their barracks and hangars and send your diplomats to the negotiating table."
Mr Putin has defied a barrage of international criticism over the crisis, with some Western leaders saying he was no longer rational.
A full-blown Russian invasion could cause massive casualties and topple Ukraine's democratically elected government.
The consequences of the conflict and resulting sanctions levied on Russia could reverberate throughout the world, affecting energy supplies in Europe, jolting global financial markets and threatening the post-Cold War balance on the continent.