Russia Unleashes Forces on Ukraine on Three Sides
A man sits outside a destroyed building in Chuhuiv, following bombings.
Moscow first struck Ukraine's military infrastructure and border guard units. Then Ukrainian forces said Russian military vehicles had crossed the border near Kharkiv in the north, Luhansk in the east, Russian-annexed Crimea in the south and from Belarus too. Belarus's authoritarian leader Alexander Lukashenko said his country's military were not involved but could be if needed.
Russian tanks were later seen on the outskirts of Kharkiv, a city of 1.4 million people. Russian forces also reportedly landed by sea at Ukraine's major port cities of Odesa on the Black Sea and Mariupol on the internal Sea of Azov.
Much of the fighting appears to be centred around the east.
Residents of Kharkiv, Ukraine's second largest city, say windows in apartment blocks were shaking from constant blasts as the Ukrainian military and Russian forces exchanged shellfire.
But clashes have have also been taking place around the capital Kyiv in the north and the southern ports of Odesa and Mariupol.
Ukraine's army said Kyiv's Boryspil international airport was among a number of airfields that had been bombed, along with military headquarters and warehouses in the big cities of Kyiv, Dnipro, Kharkiv and Mariupol.
Footage verified by the BBC showed missiles slamming into an airport in the western city of Ivano-Frankivsk.
Russia claimed to have destroyed more than 70 military targets.
People wait in a traffic jam as they attempt to leave the city of Kharkiv.
Elsewhere in the country, another traffic jam forms as people try to leave the capital Kyiv.