(Bloomberg) -- Ukrainian drones attacked a plant owned by Russia’s biggest steelmaker overnight as Kyiv continues to strike beyond its borders in a war that’s entering its third year. 

The joint operation by the Security Service of Ukraine and the country’s military intelligence sought to disrupt work at the facility in Russia’s Lipetsk owned by NLMK PJSC, said a person in the country’s intelligence services. 

A unit of NLMK’s plant caught fire early Saturday. Videos circulated showing an explosion, with each side making conflicting statements about the attack’s scale. 

The fire started at 1:40 a.m. and covered just two square meters before it was extinguished, the company said in a statement. 

The person in Ukraine’s security services said the attack damaged a coke gas cooling unit. The region’s governor, Igor Artamonov, confirmed the plant was struck by a drone, but said there was no significant impact on the operation of the facility. 

Artamonov earlier said there were no casualties.

Lipetsk is located about 400 kilometers (250 miles) northeast of the Ukrainian city of Kharkiv. NLMK is the only major Russian steel company with operations near the border. 

Its also the only big Russian steelmaker that isn’t under US or European Union sanctions, and the only one that still exports steel slabs to the EU, which provided a grace period for such shipments while imposing a wider import ban a Russian steel. 

Saturday’s incident occurred as Russia’s full-scale invasion of Ukraine crossed the two-year mark. Ukraine in recent months has used drones to attack important Russian oil-processing plants from the Black Sea to the Baltic Sea, prompting the government to weigh a plan to make it easier to deploy military-grade defenses at refineries. 

Read more: Fire Tied to Ukraine Drones Shuts Novatek Baltic Sea Fuel Plant

Russia’s Defense Ministry said that air defense systems overnight intercepted two drones over Lipetsk, where NLMK is the main employer, as well as others over the Kursk and Tula regions. 

NLMK hadn’t previously been a target of a drone attack. The person in Ukraine’s security services described it as a “legitimate target,” saying the company is working for Russia’s military industry. NLMK has previously denied working for the military, and doesn’t produce heavy steel.

Read more: Russia Mulls Tougher Defense for Refineries as Drones Strike

On Friday, Ukraine’s military said the air force shot down a Russian A-50 long-range radar detection and control aircraft, the second in as many months. The attacks come days after Russian forces captured the city of Avdiivka in eastern Ukraine after months of heavy fighting.

--With assistance from Daryna Krasnolutska.

(Updates with additional comments from regional governor in fifth paragraph.)

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