Oil depots were ablaze in both Russia and Ukraine on Wednesday as both sides escalated a drone war targeting infrastructure ahead of Kyiv’s planned spring counter-offensive to try to end Moscow’s all-out invasion.

Scores of firefighters battled a huge fire that Russian authorities blamed on a Ukrainian drone crashing into an oil terminal on Russia’s side of the bridge it built to occupy Crimea.

In Ukraine, a fuel depot was also on fire after a suspected Russian drone strike on the central city of Kropyvnytskyi.

Elsewhere in Ukraine, an administrative building in the southern Dnipropetrovsk region was hit by a drone and set on fire. Ukraine said it had shot down 21 of 26 Iranian-made drones.

The two sides have been launching long-range strikes since last week in apparent anticipation of Ukraine’s upcoming counteroffensive, expected to be one of the most decisive phases of the war.

After a lull of nearly two months, Russia fired a wave of missiles before dawn last Friday, including one that killed 23 civilians while they slept in an apartment building in the city of Uman hundreds of miles from the front.

On Saturday, a suspected Ukrainian drone strike caused a fire at a Russian oil terminal in occupied Crimea. On Monday, Russia hit dozens of homes and an industrial enterprise in the Dnipropetrovsk region that Kyiv did not identify. And blasts have derailed freight trains in Russia’s Bryansk region adjacent to Ukraine for the past two days in a row.

Moscow says its long-range attacks have struck military targets, though it has produced no evidence to support this.

Kyiv does not comment on incidents in Russia or occupied Crimea but says destroying infrastructure supporting the Russian military in Ukraine is part of the preparation for its planned ground assault, ready to begin at any time.

FIRE OF HIGHEST RANK

Flames and black smoke billowed over large tanks emblazoned with red warnings of “Flammable” in videos posted on Russian social media of the burning fuel depot near the Crimea bridge.

“The fire has been classified as the highest rank of difficulty,” Veniamin Kondratyev, the governor of the Krasnodar region said on the Telegram messaging app, adding that there were no casualties.

He said 188 firefighters were battling the blaze, attacking it with foam. He called for people to remain calm and said there was no need to order the evacuation of the nearby village of Volna.

Russia’s TASS news agency, citing emergency services, said the fire was caused by a drone falling on the facility. Moscow had also blamed a drone for a huge fire on Saturday in Crimea, in Sevastopol, naval base of Russia’s Black Sea Fleet.

In Ukraine, the governor of the central Kirovohrad region said three Russian drones had tried to hit an oil facility in the region’s main city Kropyvnytskyi. Prosecutors said a huge fire had broken out.

Ukraine says its air defences have mostly neutralised the latest attacks, especially around the capital Kyiv.

“All enemy targets were identified and shot down in the airspace around the capital,” Kyiv’s military administration said on Wednesday morning.

Air raid sirens blared for several hours in Kyiv, the surrounding region and most of eastern Ukraine, with the skies only clearing towards dawn.

Over the past five months, Ukrainian ground forces have kept mostly to the defensive, while Russia launched a huge, largely failed winter assault, capturing little new ground despite the bloodiest infantry combat in Europe since World War Two.

For its planned counterattack, Kyiv has been building up a force with thousands of fresh troops trained at Western bases and armed with hundreds of new Western-supplied tanks and armoured vehicles. Russia has dug in heavy fortifications along the length of the front line.