Russian forces invaded Ukraine from three sides, while explosions rang out in several cities, including the capital Kiev, in a wide-ranging attack that began before dawn on Thursday.
Here is a timeline of how and when it happened.
Putin announces an attack: Russian President Vladimir Putin delivered a speech early Thursday morning, saying he had decided “to carry out a special military operation…to protect people who have been victims of abuse and genocide by the Kiev regime for eight years”, repeating a baseless claim about Ukraine’s Donbass region backed by Russian separatists.
He, however, denied that Russia planned to occupy Ukrainian territories. “We will not impose anything on anyone by force.”
But in a deeply threatening passage, Putin added that anyone trying to interfere with or threaten Russia would bring “consequences you have never known in your history.”
Ukrainian President Volodymyr Zelensky responded hours later with a one-minute speech, saying he had spoken to US President Joe Biden and that the United States was mobilizing international support for Ukraine.
“The West is with us,” he said, and announced martial law across the country.
A pre-dawn assault: The invasion began hours before dawn with a series of missile attacks on locations near Kiev, as well as the use of long-range artillery against the northeastern city of Kharkiv near the Russian border.
It quickly spread through central and eastern Ukraine as Russian forces attacked the country from three sides. In the hours before daybreak, residents of the cities of Odessa, Dnipro, Mariupol and Kramatorsk reported huge explosions.
The immediate details of the casualties were unclear. The Ukrainian Ministry of Defense claimed that its troops suffered no losses.
But there was clearly extensive damage in and around several towns. In Kharkiv, video emerged of a building that had been damaged by a long-range missile or artillery. Another video showed a rocket embedded in a road. The state emergency service reported that six people were trapped in the rubble in Nizhyn.
Ukraine’s Interior Ministry said ballistic missiles were used in the offensive, while jets were heard over the central town of Zaporizhzhye.
The Russians used a wide range of weapons in their assault, including attack planes and helicopters, tanks, long-range artillery and missiles.
Dawn is rising: After dawn, aerial sirens sounded across Kiev and also in the western city of Lviv. Shortly after, a single unidentifiable plane roared over the capital.
As the day began in Kiev, streams of vehicles crossed the northern bridge, heading west, away from the center of the Russian onslaught. Other inhabitants of the capital took refuge in the metro.
Across the country, long queues have formed at gas stations and ATMs. A few people gathered in the streets of Kharkiv to pray.
Under overcast skies on Friday morning, Kiev seemed in shock. The streets were quiet and the schools closed. Here and across the country, Ukrainians are just beginning to come to terms with a cataclysmic night and the prospect of a deeply uncertain future.
CNN teams across Ukraine and Russia contributed to this report.