Russian troops enter Ukraine's Kharkiv -Ukrainian official

"The Russian enemy's light vehicles have broken into Kharkiv, including the city centre," Governor Oleh Sinegubov said. "Ukraine's armed forces are destroying the enemy. We ask civilians not to go out."

Videos published by Anton Herashchenko, adviser to the interior minister, and Ukraine's state information agency showed several light military vehicles moving along a street and, separately, a burning tank.

A witness in Kharkiv said Russian soldiers and armoured vehicles could be seen in different parts of the city and firing could be heard.

Military trucks with the letter "Z" painted on their sides could be seen in residential areas, the witness said.