Reported By BBC
Putin orders attack
In a televised speech at 05:55 Moscow time (02:55 GMT), Mr Putin announced a “military operation” in Ukraine’s eastern Donbas region. This area is home to many Russian-speaking Ukrainians. Parts of it has been occupied and run by Russian-backed rebels since 2014.
Mr Putin said Russia was intervening as an act of self-defence. Russia did not want to occupy Ukraine, he said, but would demilitarise and “de-Nazify” the country.
He urged Ukrainian soldiers in the combat zone to lay down their weapons and go home, but said clashes were inevitable and “only a question of time”.
And he added that any intervention from outside powers to resist the Russian attack would be met with an “instant” and devastating response.
Ukraine’s President Volodymyr Zelensky said Russia had carried out missile strikes on Ukraine’s infrastructure and on border guards.
Russia’s defence ministry has denied attacking Ukrainian cities – saying it was targeting military infrastructure, air defence and air forces with “high-precision weapons”.
Tanks and troops enter Ukraine
Tanks and troops have poured into Ukraine at points along its eastern, southern and northern borders, Ukraine says.
Russian military convoys have crossed from Belarus into Ukraine’s northern Chernihiv region, and from Russia into the Sumy region, which is also in the north, Ukraine’s border guard service (DPSU) said.
Belarus is a long-time ally of Russia. Analysts describe the small country as Russia’s “client state”.
Convoys have also entered the eastern Luhansk and Kharkiv regions, and moved into the Kherson region from Crimea – a territory that Russia annexed from Ukraine in 2014.
The Russian offensive was preceded by artillery fire and there were injuries to border guards, the DPSU said.
There have also been reports of troops landing by sea at the Black Sea port cities of Mariupol and Odesa in the south. A British resident of Odesa told the BBC many people were leaving.
About 10 civilians are believed to have been killed, including six in an air strike in Brovary near the capital Kyiv. A man was also killed in shelling outside the major eastern city of Kharkiv.
A Ukrainian presidential adviser said that more than 40 soldiers had died and dozens more were wounded. Ukraine said it had killed 50 Russian troops.
Ukraine fighting back
The Ukrainian armed forces said they had shot down five Russian planes and a helicopter – which Russia denies – and inflicted casualties on invading troops.
But later on Thursday President Zelensky said Ukraine had suffered losses and a lot of aircraft and armoured vehicles had been destroyed.
Russia said it has destroyed more than 70 military targets in Ukraine.
Much of the fighting appears to be centred around the east of the country. But clashes have also been taking place around Kyiv and the Black Sea port cities of Odesa and Mariupol.
Ukraine has declared martial law – which means the military takes control temporarily. It has cut diplomatic ties with Russia, offered weapons to anyone who wants them and declared an overnight curfew for Kyiv.
Meanwhile Foreign Minister Dmytro Kuleba implored the world to impose devastating sanctions, including banning Russia from the international Swift bank transfer system