Ukraine hit a big Russian ammunition depot with drones early Wednesday, with videos showing fireballs lighting up the night sky. The attack came just hours after the Russian military claimed to have captured the town of Ukrainsk, as Moscow continues a slow but steady advance in eastern Ukraine.

Control of Ukrainsk, confirmed by geolocated battlefield footage analyzed by independent groups, brings Russia one step closer to its long-held goal of seizing all of the eastern Donetsk region, which it already partly controls. Ukrainsk, once home to 10,000 residents, lies on the path to the city of Kurakhove, a defensive stronghold.

The capture of Ukrainsk and the Ukrainian drone strikes, which hit in the northwestern Russian town of Toropets and were also confirmed by verified geolocated footage, highlighted one of the main dynamics of the war in recent months: Russian forces are gaining ground in Ukraine, and Kyiv is trying to disrupt that progress by hitting military bases and warehouses that are key to Russia’s operations.

Igor Rudenya, governor of the western Russian region of Tver, which includes Toropets, said in a statement that the town had been targeted by a “massive drone attack” but did not mention the ammunition depot. He said that wreckage from a destroyed Ukrainian drone had sparked a fire.

Rudenya did not say what was burning, but the damage was significant enough that he ordered a partial evacuation of Toropets on Wednesday morning. He later announced that residents could return.

An official from the Ukrainian Security Services said that drones had hit a “large warehouse” in Toropets containing weapons such as Iskander missiles and guided bombs known as KABs. The claim could not be independently verified.

NASA satellites detected multiple fires in the area, which independent analysts monitoring open-source imagery said corresponded to the location of a big ammunition depot. The warehouse was built in 2018, according to a report by the Russian state news agency Tass, to store missiles, ammunition and explosives, with a storage capacity of several hundred tons.

Videos of the aftermath of the attack posted on social media and verified by The New York Times and independent analysts showed huge balls of flame and plumes of smoke rising from several positions across a body of water.

The smoke trails were so large that they were even picked up by weather satellites. The entire depot was still burning by midday Wednesday, according to verified satellite images. Earthquake monitoring stations also recorded a tremor in the area.

Toropets is nearly 300 miles north of Ukraine and the distance of the strike would be a testament to Kyiv’s improved long-range drone capabilities.

Battlefield analysis

Pasi Paroinen, an analyst for the Finland-based Black Bird Group, which analyzes satellite images and footage from the battlefield, said, “The depot did indeed blow up.” He added that it was “pretty certain at this point” that it was the result of a Ukrainian strike.

Yuri Podolyaka, a pro-Kremlin military blogger, wrote on social media on Wednesday that Ukraine had “struck an ammunition depot near the city of Toropets at night.”

Russia’s Defense Ministry said that the country had been attacked by dozens of Ukrainian drones overnight, adding that Russia had shot down 54 of them over different regions. The ministry did not mention the Tver region or the fires in Toropets in its report.

In recent months, Kyiv has ramped up long-range strikes on airfields, military factories and oil refineries within Russia, using homemade weapons, mostly drones. The Ukrainians have been pressing their allies to let them use Western-supplied missiles to strike deep into Russia more effectively, an authorization that has yet to be granted.

Commenting on the attack on the ammunition depot, Mykhailo Podolyak, a top Ukrainian presidential adviser, said, “Very effective, very impressive, but not enough.” Ukraine needs missiles to achieve bigger results, he said.

By striking ammunition depots and airfields behind enemy lines, Kyiv has tried to undermine Russian military operations and disrupt Moscow’s progress on the battlefield.

Since the early months of this year, Russian forces have made steady advances in eastern Ukraine, seizing cities, towns and villages in often bloody battles. After Russia’s push toward Pokrovsk, a strategic railway and road hub, stalled in recent days, the Russian military has shifted its focus to the south of that area, toward Kurakhove.

Vincent Tourret, an analyst at the French Foundation for Strategic Research, said that Russia, by pressing assaults toward Kurakhove, was trying to secure control over larger swaths of Ukrainian land. By doing so, Russian forces can position more artillery beyond the reach of Ukrainian defenses, potentially setting the stage for a renewed offensive against Pokrovsk, Tourret added.

The Ukrainian General Staff on Wednesday reported 49 Russian assaults around Kurakhove over the past day. The 46th Airmobile Brigade of Ukraine said last Thursday that Russia had launched four waves of attacks toward the city, involving a total of 46 military vehicles, including tanks. The brigade said that the attacks had been repelled, a claim that could not be independently verified.

The recent capture of Ukrainsk, which Ukraine did not comment on, could facilitate Russia’s approach to Kurakhove from the north. Russian troops have also been advancing from the east in a pincer movement, tightening pressure on the city. In the spring, Ukrainian forces built a network of trenches and anti-tank ditches around Kurakhove, anticipating future assaults after losing nearby towns.