On Monday, fierce fighting continued in east Ukraine as Moscow rejected Kyiv’s claims that it was getting ready to leave a nuclear power plant in the south of the country that it has been occupying since March.

Russia is battling to take the city of Bakhmut in the eastern Donetsk region and secure a symbolic victory after being on the back foot for months. Recent effective Ukrainian offensives have put most of the northeastern Kharkiv region back under Kyiv’s control, as well as the important southern regional capital of Kherson.

The Ukrainian military’s General Staff announced on Monday that Russia was preparing to move troops from Belarus, close to Ukraine’s northern border with a Moscow ally, onto occupied Ukrainian territory to support units that have suffered losses while battling to prevent the invasion.

Russia’s efforts to fortify defenses in occupied areas come as its military campaign, which has been ongoing for more than nine months, sputters on. The largest nuclear power plant in Europe, Zaporizhzhia, which Russia seized in March, may be ready to be abandoned, according to Petro Kotin, the head of Ukraine’s state nuclear energy company Energoatom.

In an interview with Ukrainian television, Mr. Kotin stated, “In recent weeks we’ve been getting information that signs have appeared that they may be preparing to leave.”

On Monday, the Kremlin denied that Russia was making any preparations to leave the plant’s territory. Russia has heavily fortified the plant with troops and armor, and it has long been the target of routine shelling that both sides have blamed on each other.

Dmitry Peskov, a spokesman for the Kremlin, said: “There’s no point looking for signs where there are none and there can be none.

Following Ukraine’s recent recapture of the southern Kherson region after more than eight months of occupation, Russian forces stationed across the Dnipro River have been sporadically firing artillery at the area. After Russia damaged infrastructure during its withdrawal, authorities have been able to restore electricity in some areas of the city, but essential services have still not been fully restored.

Panic over the escalating bombardment has replaced earlier this month’s scenes of jubilation as Ukraine troops entered the city of Kherson. Residents have been ordered to evacuate, and at six o’clock every evening, a free train departs the city headed west.

Volodymyr Zelensky, the president of Ukraine, issued a warning that the nation was in for a challenging week due to the possibility of additional missile strikes by Russia intended to cripple vital infrastructure and lower morale among Ukrainians.

“Our armed forces are getting ready. In his nightly address on Sunday evening, Mr. Zelensky praised the repair workers working extra hours across the nation, saying, “Our whole country is preparing. “Every scenario is being evaluated.”

As winter sets in and large portions of the nation, including its largest cities, experience prolonged power and water outages that frequently render the heating system inoperable as temperatures start to drop, Ukrainian and Western officials have warned of a potential humanitarian catastrophe in Ukraine.

“We understand that the terrorists are preparing new attacks,” Mr. Zelensky said. “We know this for sure. And while they have rockets, they will unfortunately not calm down.”

Oleksiy Reznikov, Ukraine’s defense minister, on Monday wrote on Twitter that Russia had launched 16,000 missile attacks on Ukraine over the past nine months.

For attacks that have killed civilians nationwide and damaged thousands of homes, Ukraine has labeled Russia a terrorist state. The European Parliament and national parliaments of several other countries have followed suit. Russia has criticized the designation and denied targeting civilians.

Authorities in Kyiv claim to have opened more than 430 stations where people can warm up and charge their devices and they have plans to open an additional 100. In an interview with Ukrainian media that was released on Monday, Mayor Vitali Klitschko stated that power outages would probably last until the spring and that, if the situation worsens, some residents may need to be evacuated from the city.

In a show of support, the foreign ministers of Lithuania, Latvia, Estonia, Finland, Sweden, Norway and Iceland visited Kyiv on Monday

“Despite Russia’s bomb rains and barbaric brutality Ukraine will win!” Latvia’s chief diplomat, Edgars Rinkevics, wrote on Twitter.