A third Russian airfield was ablaze on Tuesday from a drone strike, a day after Ukraine demonstrated an apparent new ability to penetrate hundreds of kilometers deep into Russian air space with attacks on two Russian air bases.

Officials in the Russian city of Kursk, located closer to Ukraine, released pictures of black smoke above an airfield in the early morning hours of Tuesday after the latest strike. The governor said an oil storage tank there had been set ablaze but there were no casualties.

It came a day after Russia confirmed it had been hit by what it said were Soviet-era drones – at Engels air base, home to Russia’s fleet of giant strategic bombers, and in Ryazan, just a few hours drive from Moscow. Kyiv did not directly claim responsibility for the strikes but celebrated them.

“If Russia assesses the incidents were deliberate attacks, it will probably consider them as some of the most strategically significant failures of force protection since its invasion of Ukraine,” Britain’s ministry of defence said on Tuesday.

“The Russian chain of command will probably seek to identify and impose severe sanctions on Russian officers deemed responsible for allowing the incident.”

Russia’s defence ministry said three service members were killed in the attack at Ryazan. Although the attacks struck military targets it characterised them as terrorism and said the aim was to disable its long-range aircraft.

The New York Times, citing a senior Ukrainian official, said the drones involved in Monday’s attacks were launched from Ukrainian territory, and at least one of the strikes was made with the help of special forces close to the base.

Ukraine never acknowledges responsibility for attacks inside Russia. Asked about the strikes, Ukrainian Defence Minister Oleskiy Reznikov repeated a longstanding joke that explosions at Russian bases were caused by careless cigarette smokers.

“Very often Russians smoke in places where it’s forbidden to smoke,” he said.

Ukrainian presidential adviser Oleksiy Arestovych went further, noting that Engels was the only base Russia has that is fully equipped for the giant bombers which Russia has used in attacks on Ukraine.

“They will try to disperse (strategic aircraft) to airfields, but all this complicates the operation against Ukraine. Yesterday, thanks to their unsuccessful smoking, we achieved a very big result,” he said.

Russian commentators said on social media that if Ukraine could strike that far inside Russia, it might also be able to hit Moscow.

“The ability of the armed forces of Ukraine to reach military targets deep in the territory of the Russian Federation has a very symbolic and important meaning,” Ukrainian military analyst Serhiy Zgurets wrote on the Espreso TV website.

The huge Tupolev long-range bombers that Russia stations at Engels air base are a major part of its strategic nuclear arsenal, similar to the B-52s deployed by the United States during the Cold War. Russia has used them in its campaign since October to destroy Ukraine’s energy grid with near weekly waves of missile strikes.

The Engels base, near the city of Saratov, is at least 600 km (372 miles) from the nearest Ukrainian territory.

Russia responded to Monday’s attacks with what it called a “massive strike on Ukraine’s military control system”. Missile strikes across Ukraine destroyed homes and knocked out power, but the impact seemed to be less severe than barrages last month that plunged millions of Ukrainians into darkness and cold.

Ukraine’s air force said it had shot down more than 60 of around 70 missiles.

A missile had torn a huge crater out of the earth in the village of Novosofiivka, about 25 km (16 miles) east of Zaporizhzhia city in southern Ukraine and completely shredded a nearby house. Ambulance workers collected two bodies lying by a destroyed car.

Olha Troshyna, 62, said the dead were her neighbours who were standing by the car seeing off their son and daughter-in-law when the missile struck. With houses now destroyed and winter setting in, she had no idea where she would go.

“We have no place to go back to,” she said. “It would be fine if it were spring or summer. We could have done something if it were a warm season. But what am I going to do now?”

Ukraine warned there would be emergency blackouts once again in several regions as it repaired damage.

At least four people were killed in Russia’s latest strikes, Ukrainian President Volodymyr Zelenskiy said.

“In many regions, there will have to be emergency blackouts,” he said in a late Monday video address. “We will be doing everything to restore stability.”

Russia, which calls the invasion a “special military operation” to root out nationalists, claims a military justification for its attacks on Ukraine’s civilian infrastructure. Kyiv says the attacks have no military purpose and are intended to hurt civilians, a war crime.

“They do not understand one thing – such missile strikes only increase our resistance,” Ukraine’s defence minister Reznikov said. “Moreover, they increase the desire of our partners to support us.”

The United States said it would convene a virtual meeting on Thursday with oil and gas executives to discuss how it can support Ukrainian energy infrastructure, according to a letter seen by Reuters.

U.S. Secretary of State Antony Blinken said Russia would fail in its “current gambit of trying to, in effect, get the Ukrainian people to throw up their hands”.