Ukrainian President Volodymyr Zelenskiy has warned of possible Russian attacks during the holiday season and urged Ukrainians to be extra vigilant in the coming days.
"With the holiday season approaching, Russian terrorists could become active again," Zelenskiy said in his evening video address on December 23.
The Ukrainian military leadership has recently warned about new missile attacks on the country's infrastructure and energy supply, noting that a Russian naval unit including a warship equipped with cruise missiles had been spotted in the Black Sea.
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Zelenskiy met with Ukrainian military leaders on December 23 after returning to Kyiv from the United States, saying the military is preparing for the coming months and next year.
"Our tasks are unchanged. This is the liberation of our land. Safety for our people. Restoration of our country after Russian strikes. These are the components of the Ukrainian victory, which we are bringing closer step by step," he said.
Pitched battles continued in the east earlier on December 23, where Moscow's offensive has centered on the cities of Bakhmut and Avdiyivka in Donetsk, Ukraine's General Staff reports, as a regional official reported that Russians are leveling a famous theater to the ground in the southern city of Mariupol.
In Washington, the House of Representatives passed a further $45 billion in aid included in an overall government spending bill and sent the measure to President Joe Biden for his signature.
Zelenskiy responded in a tweet saying he was grateful to Congress for "providing an additional $45 billion in aid to Ukraine and unwavering bipartisan support for Ukraine in the fight for freedom. It is extremely important that [Americans] are together with Ukrainians in this struggle," he added.
Zelenskiy also posted a tweet thanking Biden, saying it had been an honor to "meet with the leader of the country that helps us stand." The visit to Washington showed that the U.S. and Ukraine "stand together on the side of good, democracy and justice," he said.
Besides their incessant shelling of Bakhmut and Avdiyivka in Donetsk, where the fiercest battles have been fought in recent months, Russians kept pounding military and civilian locations in three other eastern regions -- Sumy, Kharkiv, and Luhansk, the General Staff said, adding that Ukrainian forces repelled a total of 19 attacks over the past 24 hours.
It also said that because of the significant losses suffered, the Russian military had set up a field hospital in Berdyansk in the Zaporizhzhya region, where it has also converted several tourist resorts into quarters for military personnel.
WATCH: Located less than 2 kilometers from the front line, residents of the once-thriving settlement of Velyka Novosilka in Ukraine's eastern Donetsk region endure Russian shelling by huddling together in cellars, sharing a stove, and keeping each others' spirits up.
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Lost Pets, Constant Russian Shelling: Ukrainian Town Holds Out In Donetsk Region
The General Staff also reported that in the occupied Ukrainian region of Crimea, the Russian military appears to be reinforcing defensive positions to the north -- apparently out of concern of a possible Ukrainian offensive.
In Moscow, Chief of General Staff Valery Gerasimov said the front line in Ukraine was stable, and that Russian forces had been focused on "completing the liberation" of Donetsk.
In Ukraine's southern Azov Sea port city of Mariupol, which fell earlier this year following months of resistance by Ukrainian forces, Russian troops on December 22 started demolishing the famed Donetsk Academic Regional Drama Theater, Petro Andryushchenko, an adviser to the city's mayor, said on Telegram.
The theater, a historical monument which at the start of the Russian invasion had been converted into a bomb shelter for about 600 people, including many children, was repeatedly targeted by Russian air strikes despite being clearly marked as a refuge for civilians.
"The demolition is a clear attempt to hide forever the physical evidence of the largest simultaneous deliberate killing of Ukrainians by the Russians since the beginning of this phase of the war," Andryushchenko wrote, adding that only the front part of the theater had been left intact, apparently as a basis for future reconstruction.
An investigation by the Associated Press has found that more than 10,000 new graves have appeared in Mariupol, which was virtually razed to the ground during the fighting, and the death toll might actually be three times higher than an early estimate of at least 25,000.
Furthermore, Russians plan to demolish well over 50,000 homes, AP estimated.
Zelenskiy, who was back in Kyiv from his lightning trip to the United States, vowed on his Telegram channel that "we'll overcome everything," as U.S. representatives were preparing to vote on a Senate-approved $1.66 trillion bill including an extra $45 billion for Ukraine that follows American aid worth around $50 billion sent to Kyiv this year.
An acute power shortage in Kyiv caused by Russian attacks on the Ukrainian energy grid has forced the suspension of trams and trolley buses. Mayor Vitali Klitschko announced that additional regular buses would run in their place.
The metro is not affected by the energy-saving measures, he said.