KYIV, Nov 19 (Reuters) - Ukraine used U.S. ATACMS missiles to strike Russian territory on Tuesday, taking advantage of newly granted permission from the outgoing administration of U.S. President Joe Biden 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. Debris of one hit the facility, starting a fire that was swiftly put out and caused no casualties or damage, it said.

Ukraine said it struck a Russian arms depot about 110 km (70 miles) inside Russia, an attack that caused secondary explosions. Ukraine's military did not publicly specify the weapons used, but a Ukrainian government source and a U.S. official confirmed it had used ATACMS.

A U.S. official said Russia intercepted two of eight missiles and that the strike was at an ammunition supply point.

Biden gave approval this week for Ukraine to use ATACMS, the longest-range missiles Washington has supplied, for such attacks inside Russia. Russian Foreign Minister Sergei Lavrov said the use of ATACMS was a clear signal the West wanted to escalate the conflict.

Moscow has said such weapons cannot be launched without direct U.S. operational support and their use would make Washington a direct combatant in the war, prompting Russian retaliation.

The attacks came as Ukraine marked 1,000 days of war, with a fifth of its territory in Russian hands and doubts about the future of Western support as U.S. President-elect Donald Trump heads back to the White House.

Russia's Defence Ministry also said air defence units destroyed 42 Ukrainian drones in at least eight southern and central regions between 9 p.m. and 11.55 p.m. (1800 to 2055 GMT) on Tuesday, including 32 in Bryansk region.

Ukraine has long deployed drones to hit targets deep inside Russian territory, including airfields and sites associated with energy. But the use of dozens dispatched over a short period of time was unusual.

At the United Nations in New York, Ukraine's U.N. ambassador, Sergiy Kyslytsya, read a statement from his country and 42 others and the European Union, rejecting Russia's "attempted illegal annexation" of Ukrainian territory and demanding immediate withdrawal.

"One thousand days is a tragic reminder of the need to remain resolute in ensuring ... that international law prevails, not just in Ukraine, but wherever it is challenged," he said.

Military experts say using the U.S. missiles can help Ukraine defend a pocket of captured Russian territory in the Kursk region as a bargaining chip, but was not likely to have a decisive impact on the 33-month-old war, in part as the move comes far too late.

The missile's range of up to 300 km is much shorter than some that Moscow has used to strike Ukraine, including its hypersonic Kinzhal weapon with a reported range of up to 2,000 km.

On Tuesday, Russian President Vladimir Putin signed a new nuclear doctrine that appeared intended as a warning to Washington. It lowers the threshold under which Russia might use atomic weapons to include responding to attacks that threaten its territorial integrity.

Washington said the update to the nuclear doctrine was no surprise and rejected "more of the same irresponsible rhetoric from Russia".

Zelenskiy said the step showed Putin had no interest in peace: "Especially on this day ... they presented (a) nuclear weapons strategy. Why? They didn't present (a) peace strategy. Did you hear it? ... Putin wants war."

The Pentagon said the U.S. State Department has approved another potential $100 million sale of military equipment and services to Ukraine, while Denmark said it was making a new donation of about $138 million for development of Ukraine's arms industry.

Photo from Reuters