Kyiv caused “significant” damage to a plant in Russia which produces Shahed drones used to attack Ukraine, in its deepest strike inside Moscow’s territory since the war began more than two years ago.
Ukraine used drones to mount the attack, which also targeted Taneco, Russia's third-largest oil refinery, around 1,300km from the border.
A fire broke out at the refinery, which was extinguished within 20 minutes, the Russian state RIA news agency said, adding that production had not been disrupted.
Pictures from the scene indicated the drone hit the primary refining unit, CDU-7, which accounts for around a half of the Taneco site's annual production capacity.
A Kyiv source said a Ukrainian drone attack had caused “significant damage” to a drone assembly plant.
The plant manufactures Shahed drones, which are branded as Geran-2 in Russia, according to RBC Ukraine.
The attack was among several in Tatarstan in the early hours of Tuesday.
Drones have become an increasingly important element in Ukraine’s military strategy, as Kyiv’s US and European allies remain reluctant to provide long-range missiles capable of destroying targets deep within Russia, for fear of escalation.
Ukrainian drone developers have for months been extending the weapons’ range, part of Kyiv’s effort to compensate for its battlefield disadvantage in weapons and troops.
The unmanned aerial vehicles are also an affordable option amid the months-long hold-up of $60 billion of US military aid in Congress. The delay has left Ukraine increasingly short of even basic ordnance such as artillery shells.
Neither side can currently make much of a dent on the front line that stretches more than 1,000km.
Ukraine has previously launched drone attacks in and around St Petersburg, about 1,000km north of the border.
But the facilities in Tatarstan, a province on the Volga river, appear to be Ukraine's furthest strike.
Refineries and oil terminals have increasingly become targets for Ukrainian drones in stepped-up attacks on Russian territory in recent weeks.
President Volodymyr Zelenskyy last year said Ukraine had developed a weapon that hit a target 700km away, in an apparent reference to a drone attack on Russian soil.
In 2023, Ukraine’s minister for digital transformation, Mykhailo Fedorov, said the government was intent on building a state-of-the-art “army of drones” and that its value to the war effort would be evident by the end of this year.
Ukraine trained more than 10,000 new drone pilots last year, he said.
Ukraine has also developed deadly sea drones that have struck Russian navy ships in the Black Sea.
On Tuesday, Ukraine’s air force said it had intercepted nine out of 10 Shahed drones launched overnight by Russia in the latest attack on the country’s power grid.
New EU sanctions recently took aim at Russia’s attempts to ramp up Shahed-type drone manufacturing by targeting key technology.
And last month, the UK said it would send more than 10,000 drones for use by Ukrainian armed forces throughout 2024.
Defence Secretary Grant Shapps said the UK would harness its “world-leading defence industries to deliver advanced new drone capabilities” to Ukraine.
Britain is also part of a coalition of seven countries which has pledged to send one million drones to Kyiv by increasing production.
Last month Mr Fedorov claimed Ukraine could produce two million drones a year, double the existing rate, with western financial backing.
