MOSCOW: A Ukrainian drone attack forced an oil refinery in Russia’s southern Krasnodar region to suspend operations Sunday, its operator and authorities said.

Facing a Russian offensive for over two years, Ukraine has stepped up attacks inside Russia in recent weeks, targeting energy sites in particular.

“During the night, six drones fell on the territory of the refinery in Slovyansk-on-Kuban,” Roman Siniagovski, a regional official, wrote on Telegram.

The Slavyansk-on-Kuban refinery, in the Krasnodar region east of the Sea of Azov, is one of the biggest in southern Russia.

“There have been strikes. The plant is currently at a standstill. We are assessing the damage,” Eduard Trutnev, the refinery head of security, told Interfax news agency.

A Ukrainian defence source said its forces targeted the refinery and the Kushchyovsky military airfield.

“This is the second attack by (Ukraine’s security service) drones on the Kushchyovsky military airfield and the Slovyansk refinery in the last three weeks,” the source said.

“Several aircraft were hit at the airfield” and the refinery complex was hit, the source added.

Russian drone attack injures seven in Ukraine’s Odesa, officials say

Separately, Russian air defence intercepted 57 Ukrainian drones on Saturday night, according to the Russian defence ministry.

It said nine ATACMS tactical missiles and one drone were shot down over Crimea, a peninsula annexed by Russia in 2014.

Ukrainian air attacks targeted the Russian border region of Belgorod on Sunday, according to regional governor Vyacheslav Gladkov.