A senior Ukrainian official confirmed that his military had used US-supplied longer-range ATACMS missiles to strike inside Russian territory for the first time.
"The attack on the Bryansk region was carried out with ATACMS missiles," the source told AFP, without giving further details.
Earlier, Forbes Ukraine also quoted the anonymous military source as saying Ukrainian forces had used ATACMS to hit the arsenal in Russia's Bryansk region.
When asked about an attack on a weapons depot in the Bryansk region, Ukrainian President Volodymytr Zelenskyy didn't explicitly confirm the strike, but said Kyiv now had US-made ATACMS systems as well as its own long-range capabilities, and would use all of them.
He also said that Ukraine was working with all partners to win their support for longer-range strikes, and that it was time for Germany to support Ukraine's longer-range strike capabilities against Russia.
US President Joe Biden just this week authorized Ukraine to use ATACMS, the longest-range missiles supplied by Washington, for such attacks inside Russia.
Lavrov says Ukraine's ATACMS strikes mark 'new phase' of war
Russian Foreign Minister Sergei Lavrov said Ukraine's use of longer-range ATACMS missiles against its territory marked a "new phase of the Western war" against Moscow and vowed to respond.
"We will be taking this as a qualitatively new phase of the Western war against Russia. And we will react accordingly," Lavrov told a press conference at the G20 summit in Brazil.
He said it was a clear signal that the West wanted to escalate the conflict and accused Washington of helping Kyiv operate the missiles. "Without the Americans, it is impossible to use these high-tech missiles, as (Russian President Vladimir) Putin has repeatedly said," the minister said.
Lavrov also said he hoped Moscow's new nuclear doctrine, in which Putin lowered the threshold for a nuclear strike, would be read carefully.
He added, however, that Russia would do everything possible to prevent the outbreak of nuclear war and that nuclear weapons would serve as a deterrent to nuclear war.
Former Ukrainian PM says 'it's a war against the free world'
DW spoke with former Ukrainian Prime Minister Arseniy Yatsenyuk, who said that although permission to use long-range missiles was not a "silver bullet," it did "underpin Ukraine's effort to liberate its territory and deter the Russians."
Moscow described the attack as an escalation marking a new phase in the war, even updating its nuclear doctrine to lower the threshold at which Russia would consider deploying atomic weapons — a threat which Yatsenyuk believes is a bluff.
Asked about German Chancellor Olaf Scholz's continued refusal to supply long-range German Taurus missiles to Ukraine for fear of provoking Russia further, Yatsenyuk asked rhetorically: "What other escalation can Russia commit?"
Referring not only to atrocities committed against Ukrainian civilians in occupied territories but also to "assassinations, poisonings, acts of sabotage, cyber-attacks" in western countries, he said: "Russia is already waging a proxy war against NATO."
"If Germany wants to stop this war, and if Germany wants actually to support its own security, the best response to the fully-fledged invasion waged by Russia is a full flow of support for Ukraine. Not a drip-drip approach, but full support."
Finally, Yatsenyuk called on the collective West to see the bigger picture, saying: "[Putin] is not only looking the capitulation of Ukraine but that of the entire free world — and he's not alone."
Describing the global context of Chinese and North Korean support for Russia, and Iranian support of terrorist groups like Hamas in Gaza and the Houthis in Yemen, he claimed: "This war is about more than just Ukraine. This is a war of an axis of evil, of a quartet of dictators against the free world and against your security."
US, EU, UK slam 'irresponsible' Russian nuclear rhetoric
The United States, the European Union and the United Kingdom have condemned Russia's nuclear threats as "irresponsible" after Moscow altered its nuclear doctrine in response to Ukraine's use of long-range US-supplied ATACMS missiles.
"This is more of the same irresponsible rhetoric from Russia, which we have seen for the past two years," a spokesperson for the US National Security Council told the French AFP news agency.
The spokesperson added that "we were not surprised by Russia's announcement that it would update its nuclear doctrine" and that Moscow had been "signaling its intent" to do so for several weeks.
"Observing no changes to Russia's nuclear posture, we have not seen any reason to adjust our own nuclear posture or doctrine in response to Russia's statements today," they concluded.
The EU's foreign policy chief, Josep Borrell, also accused Moscow of being "completely irresponsible," saying: "It is not the first time that Putin has played the nuclear gamble."
"Russia has subscribed to the principle that a nuclear war cannot be won, and so must never be fought," he added, warning that "any call for nuclear warfare is an irresponsibility."
British Prime Minister Keir Starmer also criticized "irresponsible rhetoric coming from Russia," saying the Kremlin's threats are "not going to deter our support for Ukraine. We need to ensure that Ukraine has what is needed for as long as it's needed to win this war."