Russian air strikes have hit cities across Ukraine, including the capital Kyiv, killing at least 13 people.
Kyiv was targeted for the first time in 51 days.
The BBC's Hugo Bachega says "Ukraine's air missile defence systems capabilities have massively improved and the vast majority of Russia's air strikes were intercepted but there could be more offensives coming".
Ukraine has been preparing for weeks for a counter offensive to take back territory and "the anticipation is high," he says.