Ukraine fired six American-supplied longer-range missiles at Russia’s Bryansk region, Moscow said Tuesday, in what would be Kyiv’s first use of the weapons inside Russia in 1,000 days of war.

The reported use of the Army Tactical Missile System, known as ATACMS, came as Russian President Vladimir Putin formally lowered the threshold for using nuclear weapons, opening the door to a potential nuclear response by Moscow to even a conventional attack by any nation supported by a nuclear power. That could include Ukrainian attacks backed by the U.S.

The developments marked a worrying new escalation in the conflict that has repeatedly ratcheted up international tensions. U.S. officials recently expressed dismay at Russia’s deployment of North Korean troops to help it fight Ukraine, while Moscow seethed when the Washington eased restrictions on the ATACMS in recent days.

The 1,000-day mark has magnified scrutiny of how the war is unfolding and how it might end, amid signs that a turning point may be coming with U.S. President-elect Donald Trump entering the White House in about two months’ time. Trump has pledged to swiftly end the war and has criticized the amount the U.S. has spent on supporting Ukraine.

Neither Russia nor Ukraine can sustain the war for a long time, analysts say, though Russia is able to keep going for longer due to its vaster resources.

Ukraine’s forces are under severe Russian pressure on the battlefield at places on the about 1,000-kilometer (600-mile) front line where its army is stretched thin. Ukrainian civilians, meanwhile, have repeatedly been clobbered by Russian drones and missiles.

On Tuesday, Ukraine claimed it hit a military weapons depot in Russia’s Bryansk in the middle of the night, though it didn’t specify what weapons it used. The Ukrainian General Staff said that multiple explosions and detonations were heard in the targeted area, around Karachev.

In a statement carried by Russian news agencies, the Russian Defense Ministry said the military shot down five ATACMS and damaged one more.

The fragments fell on the territory of an unspecified military facility, the ministry said. The falling debris sparked a fire, but didn’t cause any damage or casualties, it said.

Neither side’s claims could be independently verified.

Karachev is roughly 115 kilometers (70 miles) from the Russia-Ukraine border. Ukraine in the course of the war has been able to reach much deeper into the vast country — but with drones rather than missiles. For instance, Russian officials have reported intercepting Ukrainian drones over Moscow, which is about 500 kilometers (310 miles) from the border and most recently Izhevsk, a city about 1,450 kilometers (900 miles) from the frontier.

Earlier on Tuesday, Ukrainian officials reported a third Russian strike in as many days on a residential area in Ukraine killed at least 12 people, including a child.

The strike by a Shahed drone in the northern Sumy region late Monday hit a dormitory of an educational facility in the town of Hlukhiv and wounded 11 others, including two children, authorities said, adding that more people could be trapped under the rubble.

On Sunday, a Russian ballistic missile with cluster munitions struck a residential area of Sumy in northern Ukraine, killing 11 people and wounding 84 others. On Monday, a Russian missile barrage sparked apartment fires in the southern port of Odesa, killing at least 10 people and wounding 43.

Ukrainian President Volodymyr Zelenskyy said that the series of aerial strikes proved that Putin wasn’t interested in ending the war.

“Each new attack by Russia only confirms Putin’s true intentions. He wants the war to continue. Talks about peace are not interesting to him. We must force Russia to a just peace by force,” Zelenskyy said.

(AP)