Ukraine has steadily expanded the reach of its long-range drones, with attacks now reaching Siberia and increasing pressure on Russia's energy system, according to The Wall Street Journal.

Kyiv on Monday struck Russia's largest oil refinery in Omsk, more than 1,500 miles from Ukraine, in a strike intended to reduce fuel supplies, increase economic pressure on Moscow, and force Russia to disperse its air defenses.

The strike caused a fire at the refinery, and Ukrainian President Volodymyr Zelenskyy described the attack as "an important achievement for the armed forces of Ukraine. ... Siberia, too, is now within reach of Ukrainian precision strikes."

Iryna Terekh, CEO of the Ukrainian defense technology company Fire Point, told Reuters the Omsk refinery "had remained one of ⁠only two refineries in the top 10 that had never been hit by Ukrainian drones."

"The other is the Angarsk Petrochemical Company in Irkutsk Oblast. Both are beyond the Urals.

"It was counted on to balance out the fuel crisis after the successful ​campaign by Ukraine's defense ​forces."

Ukraine has been escalating a campaign of strikes ​against Russian oil refineries, at times causing acute fuel shortages across the country's 11 ​time zones.

The attacks are forcing Moscow to defend critical infrastructure far from the front lines while maintaining air defenses over occupied Ukrainian territory, a challenge that stretches Russian military resources.

Russian President Vladimir Putin has shrugged off Ukraine's strikes on Russian energy sites as "not critical," and insisted that the war will continue until his goals are met.

He has described the attacks on Russian energy as an effort by Ukraine to divert attention from its losses on the battlefield, although analysts say the advance of Russian forces has been stymied in recent months.

Putin appears to believe his government can keep the fuel crisis from eroding his authority and support for the war he launched by invading Ukraine more than four years ago.

At a minimum, the attacks have brought the war home for millions of Russians, undermining Putin's narrative that the conflict doesn't affect the lives of ordinary people in his country.

Reuters and The Associated Press contributed to this report.