Two Russian missiles reportedly went off their course over Ukraine and hit a Polish village, killing two people, according to news reports on November 15, citing a US intelligence official.

The report shook Poland, a Nato member, unleashing a flurry of speculation about how the alliance should respond. Officials in Poland and the US urged caution in an already tense situation on a day when Russia launched a barrage of 100 missiles over Ukraine.

"We are verifying the need to trigger Nato's Article 4 at the moment," Jacek Siewiera, the head of Poland's National Security Bureau (BBN) told reporters after a crisis meeting of the bureau convened by President Andrzej Duda and Prime Minister Mateusz Morawiecki.

The National Security Bureau meeting was due to a “crisis situation,” the government’s spokesman Piotr Muller said. 

Article 4 says that Nato member states will "consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the parties is threatened."

“A US official said missiles crossed into Nato member Poland, where two people were killed,” AP reported. The official spoke “on condition of anonymity because of the sensitive nature of the situation”.

The Russian Defence Ministry denied that it had carried out any strikes close to that part of the border, saying the claims were a “deliberate provocation with the goal of escalating the situation”.

“No strikes on targets near the Ukraine-Poland state border were undertaken with Russian weaponry,” the ministry said, adding that the footage of shrapnel found at the site of the explosion had “nothing to do with Russian weaponry”.

The Pentagon said it was "looking into" the report about the incident but had no information to corroborate that it was a Russian attack. The US State Department said the reports were "incredibly concerning",  Reuters reported, adding that Washington is trying to determine what happened and the appropriate next steps.

The barrage of Russian attacks on Ukraine on Tuesday damaged an element of the Druzhba (Friendship) oil pipeline, disrupting oil flows to Hungary, Slovakia, and the Czech Republic.