Ukrainian drones struck a major oil refinery in the city of Omsk in western Siberia, in what appears to be one of Kyiv’s deepest attacks on Russian territory since the full-scale invasion of Ukraine.

Ukraine’s military general staff said Monday that the strike caused a fire at the facility, which is situated nearly 2,500 kilometers (1,553 miles) from Ukrainian territory and close to Russia’s border with Kazakhstan.

The attack, which was confirmed by local Russian officials, provides further evidence of Kyiv’s enhanced long-range drone capabilities and comes on the eve of a crunch NATO summit. Heads of state from 32 countries are expected in Turkey’s capital from Tuesday for the two-day conference.

“Today, our long-range sanctions reached the oil refinery in Omsk – nearly 2,500 kilometres from Ukraine,” Ukrainian President Volodymyr Zelenskyy said in his daily evening address, according to a translation.

“Upgraded Fire Point drones have put Siberia within reach of Ukrainian precision. This is a significant blow to Russia’s oil economy and an important achievement for the Armed Forces of Ukraine,” Zelenskyy said.

Based in Kyiv, Fire Point is a leading Ukrainian defense-technology company that specializes in drone and missile systems for modern precision warfare.

The Omsk oil refinery represents the largest of Russia’s 11 gasoline producers to be hit by Ukrainian forces, Ukraine’s military said.

The facility is estimated to have a refining capacity of more than 21 million metric tons of crude oil per year and specializes in the production of a range of fuels, lubricants and petrochemical products.

Omsk regional governor Vitaly Khotsenko said via Telegram on Monday that emergency services were working at the scene following a Ukrainian attack at the facility. No casualties were reported from the incident.

Ukraine has stepped up its attacks on Russian oil facilities in recent months, seeking to deplete President Vladimir Putin’s war chest as the Kremlin’s more than four-year war drags on.

Russia had launched a barrage of missiles and drones against Kyiv in the early hours of Monday, killing at least 19 people, authorities said. The attack followed a separate deadly assault on Ukraine’s capital last week.

U.S. President Donald Trump held separate calls with Russia’s Putin and Ukraine’s Zelenskyy over the weekend and said Monday that a resolution to the conflict is “getting closer than people realize.”

Trump is expected to hold talks with Zelenskyy on the sidelines of the NATO summit in Ankara.