The Ukrainian military said it struck the Kirishi oil refinery in Russia's northwestern Leningrad region overnight on Sunday.

The attack caused explosions and a fire at the facility, which is one of the largest oil refineries in Russia, the Ukrainian Armed Forces said. It added that the refinery, which produces about 80 types of petroleum products, including automotive gasoline, diesel and aviation fuel, is involved in supplying the Russian army.

Russia's Defense Ministry said at least 361 drones had been shot down by Russian air defense systems, including four guided aerial bombs and a U.S.-made HIMARS missile. It did not give details about the location of the attacks. No one was injured in the Kirishi area, according to the governor of the Leningrad region.

Ukraine's drone command confirmed it attacked the refinery and said it had "carried out a successful strike."

"The most effective sanctions, the sanctions that work the fastest, are firing on Russian oil plants, on their terminals, on their oil depots," Ukrainian President Volodymyr Zelenskyy said in his nightly video. "They have significantly restricted the Russian oil industry, and this significantly limits the war." 

Zelenskyy singled out an attack last week on Russia's northwestern port of Primorsk for the first time which he said had inflicted "significant damage."

Meanwhile, an oil company in Russia's Bashkortostan region will maintain production levels despite a drone attack on Saturday, regional governor Radiy Khabirov said.

On Sunday, Zelenskyy added that Ukrainian forces had advanced in border districts of northern Sumy region, an area where Russian troops have tried for months to establish a foothold. 

On the same day, Russia reported their forces had struck temporary deployment sites of Ukrainian armed forces and foreign mercenaries, advancing into Ukrainian defensive areas. 

Rising tensions

In recent weeks, the United States has stepped up pressure on NATO countries to tighten energy sanctions on Russia in a bid to curtail its revenues and help end the conflict with Ukraine. 

President Donald Trump said on Saturday the U.S. is prepared to impose fresh energy sanctions on Russia, but only if all NATO nations cease purchasing Russian oil and implement similar measures.

The EU is sticking to its deadline to phase out Russian oil and gas imports by 2028, it decided last week, despite pressure from the U.S. to move more quickly.

(With input from agencies)