Russia-Ukraine live updates: Zelenskyy visits troops after night of Russian strikes

At least 21 Russian drones were launched overnight, Ukrainian officials said.

More than a year after Russian President Vladimir Putin launched a full-scale invasion of neighboring Ukraine, the countries are fighting for control of areas in eastern and southern Ukraine.

Ukrainian troops have liberated nearly 30,000 square miles of their territory from Russian forces since the invasion began on Feb. 24, 2022, but Putin appeared to be preparing for a long and bloody war.

Russia says Slovakia handing over fighter jets unfriendly step, violation of international obligations

Russia called Slovakia's transfer of MiG-29 fighter jets to Ukraine an unfriendly step and a step aimed at destroying bilateral relations.

"We are talking about another gross violation by the Slovak side of its international obligations to re-export Russian-made weapons and military equipment," Russia's Federal Service for Military-Technical Cooperation said in a statement.

"We regard these actions of Slovakia as an unfriendly act against the Russian Federation, aimed at destroying bilateral relations," the FSMTC said.

-ABC News' Will Gretsky

Ukraine says Russia's Bakhmut assault loses steam, counterstrike coming soon

Ukrainian troops, on the defensive for four months, will launch a long-awaited counterassault "very soon" now that Russia's huge winter offensive is losing steam without taking Bakhmut, Ukraine's top ground forces commander Colonel-General Oleksandr Syrskyi said Thursday.

"The aggressor does not give up hope of taking Bakhmut at any cost, despite the losses in manpower and equipment," Syrskyi said.

Adding, "Without sparing anything, they lose considerable strength and exhale. Very soon we will take advantage of this opportunity, as we once did near Kyiv, Kharkiv, Balaklia and Kupyansk."

-ABC News' Will Gretsky

Slovakia hands over 4 fighter jets to Ukraine

Slovakia has handed over four MiG-29 fighter jets to the Ukrainian Armed Forces, according to Slovakian Defense Minister Jaro Nad.

The remaining aircrafts promised to Ukraine will be handed over in the following weeks, Nad said.

In response to the news, Russia accused NATO and the EU of continuing to escalate the conflict in Ukraine and seeking to prolong it.

"The Russian Federation considers the transfer of four fighter jets by Slovakia to Ukraine a destructive step that runs counter to the EU's rhetoric about seeking peaceful solutions," Deputy Foreign Minister Alexander Grushko said in a statement.

Adding, "The Russian Federation will measure its reaction with the specific military activities of NATO on the territory of Finland."

-ABC News' Will Gretsky

1 dead, 33 injured in Zaporizhzhia missile strike

One person is dead and 33 others were injured after a missile strike hit the Ukrainian city of Zaporizhzhia, according to the head of Zaporizhzhia's regional military administration Yurii Malashko.

Among the victims are two children, who are 7 and 9 years old. Eleven adults were hospitalized, with four in serious condition, according to the secretary of the city council, Anatoly Kurtev.

-ABC News' Will Gretsky