Volodymyr Zelensky said up to 3,000 Ukrainian troops have been killed since Vladimir Putin ordered the invasion of Ukraine on 24 February, with no total yet available for civilian casualties, as fighting intensified in the battle for the southern city of Mariupol.

Ukraine’s president said the military situation in the south and east was “still very difficult”, while praising the work of his armed forces. “The successes of our military on the battlefield are really significant, historically significant. But they are still not enough to clean our land of the occupiers,” he said in a late-night video address, calling again for allies to send heavier weapons and for an international embargo on Russian oil.

Zelenskiy, speaking to CNN’s Jake Tapper, assessed that about 10,000 of his soldiers had been injured in the war so far, and that up to 20,000 Russian soldiers had died. Moscow said last month that 1,351 Russian soldiers had been killed and 3,825 wounded. There is no way yet to independently verify either claim.

Ukrainian forces remain braced for Russian reprisals after the sinking of flagship cruiser the Moskva, the pride of Russia’s Black Sea fleet, which US defence officials confirmed had sunk after a Ukrainian missile strike.

The government in Kyiv said it had destroyed the giant missile cruiser during a combat operation in the Black Sea on Wednesday. The boat’s ammunition deck exploded after it was hit by two Neptune anti-ship missiles, it added.

Russia said that since the sinking, it had struck what it described as a factory on the outskirts of the capital Kyiv that made and repaired anti-ship missiles.