Ukraine on Saturday said it hit one of Russia's largest steel plants with a drone strike on the second anniversary of Moscow launching its invasion.
Russia reported a fire in the huge Novolipetsk (NLMK) factory in the western Lipetsk region, with images on social media showing a huge blaze.
If confirmed, the attack would be the latest in Ukraine's stepped-up campaign against targets deep inside Russia.
Ukraine's SBU security service claimed the attack and said the plant was making weapons for the army to use in Ukraine.
"The drone strike on the Novolipetsk steel plant was organized by two Ukrainian special services at once: The SBU and the (military intelligence) GUR," the SBU said.
On its website, NLMK calls itself "Russia's biggest producer of steel".
The Russian army earlier said that it had at night intercepted two drones over the Lipetsk region as well as a drone over the southern Kursk region.
Lipetsk region governor Igor Artamanov had said security services were on alert at night after a "fire in one of the workshops at NLMK" before saying that the "fire had been put out".
He called on people "not to give in to panic and trust only official information" after social media footage showed a significant blaze.
Kyiv has vowed to keep attacking targets in Russia during the invasion.
