Moscow has accused Ukraine of carrying out an air attack on a fuel depot in Russia – in the first claim of an air strike on its soil since Vladimir Putin began his invasion in late February.
Russia has said before that it has experienced cross-border shelling, but not an incursion of its airspace.
A fiery explosion rocked the fuel depot in the city of Belgorod, 21 miles from the border of Ukraine, and a Russian official said two Ukrainian military helicopters were involved.
But Kyiv denied carrying out an attack. “For some reason they say that we did it, but in fact this does not correspond with reality,” said Oleksiy Danilov, secretary of Ukraine’s national security council.
Defense ministry spokesperson Oleksandr Motuzyanyk said: “Ukraine is currently conducting a defensive operation against Russian aggression on the territory of Ukraine, and this does not mean that Ukraine is responsible for every catastrophe on Russia’s territory.”
Video footage of the purported attack showed what looked like several missiles being fired from a low altitude, followed by an explosion, but the claims could not be independently verified.
Regional governor Vyacheslav Gladkov said on the messaging app Telegram that a blaze caused by the missiles had injured two workers, and some areas of the city were evacuated.
But Russian oil firm Rosneft, which owns the depot, said no one was hurt in the fire, giving no comment on the cause.
The city mayor’s office said that more than 300 firefighters battled the blaze using a helicopter and a special firefighting train.
Mr Gladkov posted photos of craters and metal fragments in a rural area where he said explosions had damaged a power line and broken a window.
Hours after the reported attack on the oil depot, a witness reached by telephone in Belgorod, who asked not to be identified, said aircraft were flying overhead and there were continuous explosions from the direction of the border.
Any airborne attack inside Russia would be likely to require skillful flying to avoid the country’s air defenses.
The explosion drew a muted response from the Kremlin, with spokesman Dmitry Peskov saying it was not helpful for talks.
This is the first time Ukraine has been directly accused of carrying out a large attack on Russian soil since the deadly invasion of the country began on 24 February, which has displaced more than 10 million people and killed thousands.
Earlier incidents in the Belgorod region had caused alarm locally but had little wider resonance in the context of the war. On the first day of the war, three people were reported to have been injured from shelling, although there was no independent confirmation. Russia said two adults and one child were injured, and an attempted murder probe was launched.
An ammunition depot caught fire on Wednesday, causing a series of blasts.
Russia, which calls its action in Ukraine “a special military operation” has lost between 7,000 and 15,000 soldiers since the war began, according to latest Nato estimates.
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Additional reporting by agencies