Local authorities in Russia claimed on Friday that Ukrainian helicopters hit an oil refinery close to the border.
A fire broke out due to an explosion at the facility after the strike, said a statement by Vyacheslav Gladkov, governor of the western Belgorod region.
The helicopters entered the region's airspace and struck the refinery at a low altitude some 40 kilometers (25 miles) from the border, Gladkov said, adding that nobody had been killed or injured in the attack.
Almost 200 firefighters have been deployed to help contain the blaze, according to Russian news agency TASS.
"Eight fuel tanks are currently on fire. A foam attack is underway. A firefighting train has engaged. Some 194 people and 59 units of equipment are operating at the site of the fire," the agency reported, citing the country's Ministry of Emergency Situations.
Ukraine ‘neither confirm nor deny’ strike
Meanwhile, according to Ukraine’s state news agency Ukrinform, Oleksandr Motuzianyk, spokesman for the Ukrainian Defense Ministry, said at a briefing when asked whether Ukraine was involved in the incident: "I want to emphasize that as of today the Ukrainian state is conducting a defense operation to repel Russian armed aggression on Ukrainian territory.”
“And this does not mean that Ukraine should be responsible for all miscalculations and all catastrophes, all events taking place in Russia,” the agency reported citing Motuzianyk.
“Therefore, I will neither confirm nor deny this information,” he added.
Statement by Russia's Defense Ministry
The Russian Defense Ministry late Friday said the oil refinery in Belgorod that was hit by Ukrainian army helicopters was not associated with the Russian army.
"Some fuel tanks were damaged and caught fire after they were hit by missiles. The facility in question was used to supply fuel for civilian vehicles. The oil refinery has nothing to do with the Russian Armed Forces," spokesman Igor Konashenkov said at a news conference in Moscow.
The Russian war against Ukraine, which started Feb. 24, has been met with international outrage, with the EU, US, and Britain, among others, implementing tough financial sanctions on Moscow.
At least 1,232 civilians have been killed in Ukraine and 1,935 injured, according to UN estimates, with the true figure feared to be far higher.
More than 4 million Ukrainians have also fled to other countries, with millions more internally displaced, according to the UN refugee agency.