CNN teams in Kyiv reported hearing explosions in the early hours of Saturday morning, with chief international correspondent Clarissa Ward describing "a nonstop volley ... of just heavy booms in the distance," continuing for several minutes.
It's not clear whether the explosions were Russian or Ukrainian strikes, she said.
Fighting is continuing on the outskirts of the Ukrainian capital, with the city's administration saying areas to the north remain the most dangerous, including the suburbs of Bucha, Irpin and Hostomel, as well as the district of Vyshorod further north of Kyiv. Fighting has also escalated in Brovary, across the Dnieper River, east of the city.
As Russian forces press in from several directions, "the worry becomes ... that the intention is to fully surround the city, to starve the city, to bombard the city and then ultimately to try to overthrow (Ukrainian President Volodymyr) Zelensky's government," Ward said.
Kyiv Mayor Vitali Klitschko told CNN the city currently only has resources — including food and medical supplies — for one to two weeks.
CNN's Ward added that "Ukrainian forces are everywhere" in Kyiv. "They have dug up defensive positions along all the main thoroughfares leading into the city, they've put tank traps around. This is a heavily fortified city now. And even if Russian forces are enable to encircle it, it will still be an almighty battle for them to get to the heart of it."