KYIV, Ukraine — The Ukrainian military might decide to pull troops back from the key stronghold of Bakhmut, an adviser to Ukraine’s president said Wednesday as Russia pursued a bloody, months-long offensive to capture the city.

“Our military is obviously going to weigh all of the options. So far, they’ve held the city, but if need be, they will strategically pull back,” an economic adviser to President Zelensky, Alexander Rodnyansky, told CNN. “We’re not going to sacrifice all of our people just for nothing.”

The battle for Bakhmut, in eastern Ukraine’s Donetsk province, has become a symbol of Ukrainian resistance as defenders hold out against relentless shelling and Russian troops suffer heavy casualties in the campaign to take the city.

Mr. Rodnyansky noted that Russia was using the best troops of the Wagner Group to try to encircle the city. The private military company known for brutal tactics is led by Yevgeny Prigozhin, a rogue millionaire with longtime links to President Putin.

Mr. Prigozhin said Wednesday that he so far had seen no signs of a Ukrainian withdrawal from the city. He maintained that Kyiv has in fact been reinforcing its positions there.

“The Ukrainian army is deploying additional troops and is doing what it can to retain control of the city,” Mr. Prigozhin said. “Tens of thousands of Ukrainian soldiers are offering fierce resistance, and the fighting is getting increasingly bloody by day.”

Recent drone footage shows the scale of devastation in the city, while Mr. Zelensky has described it as “destroyed.”

Since invading Ukraine a year ago, Russia has bombarded various cities and towns that it wanted to occupy. It also targeted Ukraine’s power supply with missile strikes ahead of winter in an apparent attempt to weaken local morale.

While Western analysts have warned that warmer weather might give Moscow an opportunity to launch a renewed offensive, Ukrainian officials nonetheless celebrated Wednesday what is regarded nationally as the first day of spring.

Foreign Minister Dmytro Kuleba announced that his country had survived Mr. Putin’s “winter terror.”

“We survived the most difficult winter in our history,” Mr. Kuleba wrote on Facebook.

The war could become a protracted conflict, analysts say, and Latvia’s prime minister, Krisjanis Kariņs, said that would demand a response from Kyiv’s Western allies.

“This is potentially for many years to come where we will have to readapt our militaries, our military industry, to be able to step up to a much, much bigger challenge,” Mr. Kariņs said after talks in Berlin with Chancellor Scholz.

Meanwhile, one of Mr. Zelensky’s top advisers, Mykhailo Podolyak, denied on Wednesday that Ukraine had used drones to attack Russian territory following Russian official statements that Ukraine had targeted infrastructure deep inside Russia.

“Ukraine does not strike on the territory of the Russian Federation. Ukraine is waging a defensive war with the aim of de-occupying all its territories,” Mr. Podolyak wrote on Twitter, suggesting the targeting of Russian infrastructure was the result of “internal attacks.”

Ukraine’s western allies have discouraged Ukraine from attacking targets in Russia proper to avoid escalation of the conflict, and Mr. Podolyak’s statement could reflect an attempt by Kyiv to maintain a degree of deniability in view of those Western concerns.

In the past, Ukrainian officials have stopped short of claiming responsibility for attacks in Russia, but also insisted that Ukraine has the right to strike any target on Russian territory in response to its aggression.

Asked about Mr. Podolyak’s denial, a Kremlin spokesman, Dmitry Peskov, said, “We don’t believe it.”

Pictures of a drone that fell near the village of Gubastovo, less than 60 miles from Moscow, showed it was a small Ukrainian-made model with a reported range of up to 500 miles, but no capacity to carry a large load of explosives.

Russia’s Defense Ministry said Wednesday it prevented a major drone attack on Crimea. According to Russian state media, six drones were shot down by air defense forces, while four more were disabled by electronic warfare systems.

In Ukraine, at least nine civilians were killed and 12 others were wounded across the country on Tuesday, the Ukrainian president’s office reported Wednesday morning.

Three people, including a 1-year-old boy, were wounded in Russian shelling of Ukraine’s southern Kherson province on Wednesday, regional officials reported.

Fierce fighting also continued in Donetsk province, with Bakhmut, the cities of Avdiivka and Vuhledar, and 17 towns and villages, coming under intense Russian shelling.