Kharkiv region head Oleg Synegubov said on Tuesday that Russian missile attacks hit the centre of Ukraine's second-largest city, including residential areas and the regional administration building, as Moscow started day six of its invasion.

Synegubov said Russia launched GRAD and cruise missiles on Kharkiv but that the city defence was holding.

Wearing a flak jacket and a helmet, Synegubov said in a video posted on social media on Tuesday morning that it was too early to know the number of casualties.

He shared a video showing Kharkiv regional administration building being hit by a missile and exploding. Reuters verified the authenticity of the video.