As Russian and Ukrainian forces fight on the ground, their leaders spar with words. Each side is claiming major victories that the other will not concede. The latest disagreement centers on the sunken flagship of Russia's Black Sea Fleet.

Russia's defense ministry claims the ship went down in a "heavy storm," with no mention of any attack. Ministry officials have said a fire caused the ammunition stored on board to explode.

But a Ukrainian governor says the damage came from his side's missiles.

The US Defense Department called the sinking a major blow to Russia.

In a CNN program on Thursday, Pentagon Press Secretary John Kirby said the ship played an important role in Russia's naval strategy.

Russians are boasting of progress on other fronts. Their troops have faced resistance in the battle for the port city of Mariupol.

Russian defense ministry officials now say that more than 1,100 Ukrainian troops have surrendered.

Russia continues to ramp up its assault on the east. Facing accusations of targeting civilians, officials say shells fired in the regions of Donetsk and Odesa are hitting military assets.

The governors of these areas in western Russia say Ukraine has sent their missiles across the border -- an action that could provoke a retaliatory strike on Kyiv. But the Ukrainians deny the accusation.

It has now been 50 days since Russian invaded.

Ukraine's President Volodymyr Zelenskyy told his people that the defense of their homes has not gone unnoticed by the rest of the free world.

In a video released by the presidential site, Zelenskyy said, "You have all become heroes. All Ukrainian men and women who withstood and do not give up. And who will win. Who will return peace to Ukraine." He added that Russians will be held to account.

UN officials are still struggling to figure out how many civilians have been killed in Ukraine since the fighting began. The official count is inching closer to 2,000.

But that doesn't include the tens of thousands of people Ukrainians say have died in Mariupol, and other cities devastated by ongoing attacks.

The intensity of the fighting has made it impossible to confirm those reports.