Ukraine said Wednesday that its forces struck one of Russia's largest oil refineries overnight, intensifying military and economic pressure on Moscow just hours after President Volodymyr Zelenskyy met US President Donald Trump in Washington.

Ukraine's General Staff said the overnight drone strike set fire to the Ryazan oil refinery, one of Russia's largest refining facilities, with an annual processing capacity of about 17 million tons of crude oil. The plant produces gasoline, diesel, aviation fuel and other petroleum products.

The refinery is located in Russia's Ryazan region, roughly 400 kilometres from the Ukrainian border.

The latest attack is part of Ukraine's sustained campaign of long-range drone and missile strikes targeting Russia's energy infrastructure. Kyiv has increasingly relied on domestically developed weapons to hit oil depots and refineries deep inside Russian territory, seeking to disrupt fuel supplies and increase economic pressure on the Kremlin.

The strike came hours after Zelenskyy's visit to Washington, where he held talks with Trump as Ukraine seeks continued US military, financial and diplomatic support in its war against Russia.

Ryazan regional governor Pavel Malkov said six people were hospitalized following the drone attack. He said debris from downed drones caused fires at several unspecified industrial facilities but did not directly confirm damage to the refinery.

In a social media post, Zelenskyy said Russia must continue to bear increasing costs for the war.

"Russia must feel that every day of this war will only come at a higher cost for it. We need to weaken the aggressor and keep up the pressure to bring an end to this war closer," he said.

Ukraine's recent long-range strikes against Russian military and energy targets have been viewed as a demonstration of its growing domestic defense capabilities. The operations have also helped strengthen support in Washington after uncertainty earlier in Trump's second term over the future of US assistance to Kyiv.