Heavy rocket and artillery attacks hit several regions of Ukraine overnight on Tuesday and into Wednesday.
In the eastern Donetsk region, Ukraine's military said it impeded Russian advances towards several towns as Russia continued to try to attack Ukrainian lines.
Ukrainian President Volodymyr Zelensky has said that annexed Crimea must be liberated to end the war with Russia.
His comments came after explosions rocked the area of a Russian military air base in Crimea, killing at least one person.
Ukraine has not claimed responsibility and is not known to have attacked Crimea since Russia's invasion began.
Ukraine hit Russian targets in Henichesk, in the southern Kherson region, some 201 kilometers from the nearest Ukrainian front line.
It appears to be Ukraine's deepest attack so far into Russian-occupied territory.
The G7 nations are demanding that Russia return full control of the Zaporizhia nuclear plant and other nuclear facilities to Ukraine, amid growing concern of a disaster.
A European Union ban on Russian coal imports began on Wednesday, a move the European Commission said would affect Russian exports worth some €8 billion a year.
