Ukraine used US ATACMS missiles to strike Russian territory for the first time on Tuesday, Moscow said, in an attack regarded by Russia as a major escalation on the war's 1,000th day.

Russia said its forces shot down five of six missiles fired at a military facility in the Bryansk region, while debris of one hit the facility, causing no casualties or damage, Reuters reported. 

Ukraine said it had struck a Russian arms depot around 110 km (70 miles) inside Russia and caused secondary explosions. It did not specify what weapons it had used.

President Joe Biden gave approval just this week for Ukraine to use the medium-range US missiles for such attacks, which Moscow has described as an escalation that would make Washington a direct combatant in the war and prompt retaliation.

Meanwhile, President Vladimir Putin on Tuesday formally lowered the threshold for Russia’s use of its nuclear weapons over Biden’s decision.  

Putin has previously warned the US and other NATO allies that allowing Ukraine to use Western-supplied longer-range weapons to hit Russian territory would mean that Russia and NATO are at war.