The drone did not inflict any damage,Vorobyov said,but it likely targeted “a civilian infrastructure object”.

Pictures of the drone showed it was a small Ukrainian-made model with a reported range of up to 800km but no capacity to carry a large load of explosives.

Russian forces early on Tuesday shot down another Ukrainian drone over the Bryansk region,local Governor Aleksandr Bogomaz said in a Telegram post.

Three drones also targeted Russia’s Belgorod region on Monday night,with one flying through an apartment window in its namesake capital,local authorities reported. Regional Governor Vyacheslav Gladkov said the drones caused minor damage to buildings and cars.

The Russian Defence Ministry said Ukraine used drones to attack facilities in the Krasnodar region and neighbouring Adygea. It said the drones were brought down by electronic warfare assets,adding that one of them crashed into a field and another diverted from its flight path and missed an infrastructure facility it was supposed to attack.

Russia’s state RIA Novosti news agency reported a fire at the oil facility,and some other Russian reports said that two drones exploded nearby.

While Ukrainian drone strikes on the Russian border regions of Bryansk and Belgorod have become a regular occurrence,other strikes reflected a more ambitious effort.

Some Russian commentators described the drone attacks as an attempt by Ukraine to showcase its capability to strike areas deep behind the lines,foment tensions in Russia and rally the Ukrainian public. Some Russian war bloggers described the raids as a possible rehearsal for a bigger,more ambitious attack.

Russia hawks called for a strong retaliation. Igor Korotchenko,a retired Russian army colonel turned military commentator,called for a punishing strike on the Ukrainian presidential office in Kyiv.

Another retired military officer,Viktor Alksnis,noted that the drone attacks marked the expansion of the conflict and criticised Putin for failing to deliver a strong response.

Also on Tuesday,the authorities reported that airspace around St Petersburg,Russia’s second-largest city,was temporarily closed,halting all departures and arrivals at the city’s main airport,Pulkovo. It did not give a reason for the move,but some Russian reports claimed that the move was triggered by an unidentified drone.

The Russian Defence Ministry said it was conducting air defence drills in western Russia.

Last year,Russian authorities repeatedly reported shooting down Ukrainian drones over annexed Crimea. In December,the Russian military said Ukraine used drones to hit two bases for long-range bombers deep inside Russian territory.

Speaking at Russia’s main security agency,the FSB,Putin urged the service to tighten security on the Ukraine border.

In another development that fuelled tensions across Russia on Tuesday,an air raid alarm interrupted the programming of several TV channels and radio stations in several regions.

Russia’s Emergency Ministry said in an online statement that the announcement was a hoax “resulting from a hacking of the servers of radio stations and TV channels in some regions of the country.”

‘City is on fire’

In Ukraine,Russian forces have pressed forward their weeks-long drive to encircle and capture the eastern city of Bakhmut,where the commander of Ukraine’s ground forces described the situation as “extremely tense”.

Taking Bakhmut,the scene of some of the war’s bloodiest battles,would be Russia’s first major prize in more than six months and open the way to seizing the last remaining urban centres in the Donetsk region,one of four Moscow claims to have annexed in its “special military operation” in Ukraine.

Around Bakhmut,Russian troops,including mercenary fighters from the Wagner Group,are trying to cut the Ukrainian defenders’ supply lines and force them to surrender or withdraw.

“Despite significant losses,the enemy threw in the most prepared assault units of Wagner,who are trying to break through the defences of our troops and surround the city,” Ukraine’s Colonel General Oleksandr Syrskyi said.

An unnamed soldier from Ukraine’s 93rd Separate Mechanised Brigade,speaking on the Telegram messaging app as explosions boomed in the background,struck a defiant note:“February 28,the town of Bakhmut. The city is on fire,the enemy is pressing. Everything will be Ukraine...”

Russia’s state-run RIA news agency released a video clip it said showed Russian Su-25 fighter jets roaring over Bakhmut. “We are glad they are ours,” says a man in the clip identified as a Wagner fighter,adding the jets helped them “psychologically”.

Ukraine’s military said Russia was shelling settlements around Bakhmut,which had a pre-war population of around 70,000 but now lies in ruins after months of intense trench warfare.

“Over the past day,our soldiers repelled more than 60 enemy attacks,” the military said early on Tuesday,including on the villages of Yadhidne and Berkhivka just north of Bakhmut.

A Reuters reporter who visited the area on Monday said he saw no sign of Ukrainian forces withdrawing and that reinforcements were arriving despite constant Russian shelling.

Ukraine’s eastern front line resembles “a grinding slog” and Russia is not likely to be able to make significant territorial gains in the near term,the US undersecretary of state for defence policy,Colin Kahl,said.

“So you may see small portions of territory change hands in the coming weeks and months. I do not think that there’s anything I see that suggests the Russians can sweep across Ukraine and make significant territorial gains anytime in the next year or so,” Kahl told a House of Representatives hearing.

AP,Reuters

Get a note directly from our foreigncorrespondentson what’s making headlines around the world.Sign up for the weekly What in the World newsletter here.