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Ukraine has fired US-supplied longer-range missiles at a target inside Russian territory for the first time, a day after Washington gave its permission for such attacks.

US officials confirmed use of the Army Tactical Missile System (Atacms) to CBS news, the 91�ȱ�'s US partner.

Russia's defence ministry earlier said the strike targeted the Bryansk region bordering Ukraine to the north on Tuesday morning.

Five missiles were shot down and one damaged, with its fragments causing a fire at a military facility in the region, the ministry said.

Russia’s foreign minister Sergey Lavrov accused Washington of trying to escalate the conflict.

"That Atacms was used repeatedly overnight against Bryansk Region is of course a signal that they [the US] want escalation," he said.

"And without the Americans, use of these high-tech missiles, as Putin has said many times, is impossible."

He said Russia would "proceed from the understanding" that the missiles were operated by "American military experts".

"We will be taking this as a renewed face of the western war against Russia and we will react accordingly," he told a press conference at the G20 in Rio de Janeiro.

Earlier on Tuesday, the Kremlin approved changes to Russia’s nuclear doctrine, setting out new conditions under which the country would consider using its arsenal.

It now says an attack from a non-nuclear state, if backed by a nuclear power, will be treated as a joint assault on Russia.

Ukraine has already been using Atacms in Russian-occupied areas of its own territory for more than a year.

The missiles can hit targets at a range of up to 300km (186 miles) and are difficult to intercept.

Kyiv is now able to strike deeper into Russia using the missiles, including around the Kursk region, where Ukrainian forces hold over 1,000 sq km of territory. Ukrainian and US officials reportedly expect a counter-offensive in the region.

In a statement, Russia’s defence ministry said the strike was launched at 03:25 (00:25 GMT).

A fire caused by fallen debris from one of the missiles was quickly extinguished and there were no casualties, it said.

Ukraine’s military earlier confirmed that it had struck an ammunition warehouse in the Russian region of Bryansk, but it did not specify whether Atacms were used.

It said the attack, on a depot around 100km from the border near the town of Karachev, caused 12 secondary explosions.