Conflict raged northwest of Kyiv on Saturday and other cities were encircled and under heavy shelling, while Ukrainian officials said fighting and threats of Russian air attacks were endangering attempted evacuations.
Ukraine’s Deputy Prime Minister Iryna Vereshchuk had said the government planned to use agreed humanitarian corridors out of the besieged southern port city of Mariupol as well as towns and villages in the regions of Kyiv, Sumy and some other areas.
But the governor of the Kyiv region said fighting and threats of Russian air attacks were continuing during evacuation attempts and the Donetsk region's governor said constant shelling was complicating bringing aid into Mariupol.
An adviser to the Ukrainian presidency said earlier that 79 evacuation buses and two trucks with humanitarian cargo had left for Sumy on Saturday. Buses and trucks also left Zaporizhzhia for Mariupol, a video released by the deputy head of the Ukrainian presidential administration on social media showed.
At least 1,582 civilians in Mariupol have been killed as a result of Russian shelling and a 12-day blockade, the city council said in an online statement on Friday. It was not possible to verify casualty figures.
Air raid sirens blared across most Ukrainian cities on Saturday morning urging people to seek shelters, local media reported.
Russian rocket attacks destroyed a Ukrainian airbase and hit an ammunition depot near the town of Vasylkiv in the Kyiv region on Saturday morning, Interfax Ukraine quoted Vasylkiv Mayor Natalia Balasynovych as saying.
Ukraine's foreign ministry said a mosque in Mariupol where more than 80 people had been sheltering had also been shelled, without saying whether anyone had been killed or wounded.
Moscow has denied targeting civilians what it calls a special operation to demilitarise Ukraine and unseat leaders it refers to as neo-Nazis. It has not responded to Ukrainian challenges to provide evidence.
Ukraine said it expected a new wave of attacks on the regions around the capital Kyiv, the country's second city Kharkiv and Donbas in the east, where Russian-backed separatists have expanded their control.
Britain's defence ministry said on Friday that Russian forces could target the capital Kyiv in a few days. In an update on Saturday, it said fighting northwest of the capital continued, with the bulk of Russian ground forces 25 km (16 miles) from the centre.
The cities of Kharkiv, Chernihiv, Sumy and Mariupol remained encircled under heavy Russian shelling, it said.
Russian President Vladimir Putin launched the invasion on Feb. 24 in an operation that has been near-universally condemned around the world and that has drawn tough Western sanctions on Russia.
The bombardment has trapped thousands of people in besieged cities and sent 2.5 million Ukrainians fleeing to neighbouring countries.