Ukraine's President Volodymyr Zelenskiy said on Tuesday, without producing evidence, that Russian missiles had hit Poland, a NATO country, in what he called a "significant escalation" of the conflict.
"Russian missiles hit Poland, the territory of our friendly country. People died," Zelenskiy said in his nightly video address.
Two people were killed in an explosion in Przewodow, a village in eastern Poland near the border with Ukraine, local firefighters said on Tuesday.
The cause remained unclear. Russia's defence ministry denied reports that Russian missiles had hit Polish territory, describing the reports as "a deliberate provocation aimed at escalating the situation".
In Washington, the Pentagon and the U.S. State Department said they could not confirm Russian missiles had landed on Polish territory but were investigating.
On Tuesday, Russia had launched more than 100 missile and drone attacks on Ukraine in the latest escalation of its invasion. Zelenskiy said that only about 10 hit their targets.
"The longer Russia feels impunity, the more threats there will be to anyone within reach of Russian missiles. To fire missiles at NATO territory! This is a Russian missile attack on collective security! This is a very significant escalation. We must act," he said.
Poland is a member of the U.S.-led Western military alliance NATO, which is committed to collective defence, and the possibility that the Polish explosion resulted from an intentional or accidental Russian strike raised alarm.
"Today happened what we were warning about for a long time: We told that terror is not confined to our state borders," Zelenskiy said.
"I now want to tell every one of our Polish brothers and sisters – Ukraine will always support you. Free people won't be cowed by terror. Victory is possible when there is no fear. And we and you are not afraid."
(Reporting by Bogdan Kochubey, Lidia Kelly, Elaine Monaghan and Ronald Popeski; Writing by Lidia Kelly in Melbourne; Editing by Jonathan Oatis and Rosalba O'Brien)
