Explosions have been heard in Kyiv as Russian troops approach Ukraine's capital.

 In the early hours of Saturday morning, CNN teams in Kyiv reported hearing explosions, with chief international reporter Clarissa Ward describing "a constant salvo... of just heavy booms in the distance" that lasted several minutes.

She claimed it's unclear whether the explosions were caused by Russian or Ukrainian strikes.

Fighting has continued on the outskirts of Kyiv, with the city's government claiming that the areas to the north are the most dangerous, including the Bucha, Irpin, and Hostomel neighborhoods, as well as the district of Vyshorod farther north. Fighting has also erupted in Brovary, which is located east of the city and is located across the Dnieper River.

"The danger becomes... that the aim is to entirely surround the city, starve the city, bombard the city, and then try to overthrow (Ukrainian President Volodymyr) Zelensky's government," Ward warned as Russian forces pressed in from many directions.

Vitali Klitschko, the mayor of Kyiv, told CNN that the city only had enough food and medical supplies to last one to two weeks.

According to CNN's Ward, "Ukrainian military are everywhere" in Kyiv. "They've dug up defensive positions along all of the city's key thoroughfares, and they've set up tank traps. This city is now highly fortified. Even if Russian forces are able to encircle it, getting to the heart of the problem will be a titanic battle."