KYIV, Ukraine (AP) — Ukraine claimed responsibility Tuesday for an overnight drone attack on a Russian oil facility that started a massive blaze in the latest long-range strike by Kyiv’s forces on a border region.

Ukraine has in recent months stepped up aerial assaults on Russian soil, targeting refineries and oil terminals in an effort to slow down the Kremlin’s war machine. Moscow’s army is pressing hard along the front line in eastern Ukraine, where a shortage of troops and ammunition in the third year of war has made defenders vulnerable.

The attack set fire to an oil reservoir in Russia’s Rostov region and more than 200 firefighters were at the scene, according to Rostov Gov. Vasily Golubev.

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The blaze covered an area of 5,000 square meters (55,000 square feet) but there were no casualties, Russia’s Emergencies Ministry said.

A Ukrainian official, speaking on condition of anonymity because he was not authorized to give the information to the media, said the attack was a special operation of Ukraine’s Security Service, known as SBU. The drones targeted two Rostov oil depots that have 22 oil reservoirs, the official said.

It was not possible to independently confirm the claim.

Kyiv officials normally decline comment about attacks on Russian territory, though they sometimes refer obliquely to them.

Ukrainian drone developers have been extending the weapons’ range for months, as Kyiv attempts to compensate for its battlefield disadvantage. The unmanned aerial vehicles are also an affordable option while Ukraine waits for the arrival of more Western military aid.