Andrzej Duda tweeted that officials had "no proof at the moment that it was a missile fired by the Russian side", according to Sky News.

He added: "There are many indications that it was an air defence missile, which unfortunately fell on Polish territory."

Nato Secretary General Jens Stoltenberg said in a statement to the media: "Yesterday's explosion took place as Russia launched a massive wave of rocket attacks across Ukraine.

"An investigation into this incident is ongoing, and we need to await its outcome.

"But we have no indication this was the result of a deliberate attack and we have no indication Russia is preparing offensive military actions against Nato."

Ukraine's President Volodymyr Zelenskyy has said he has "no doubt" the missile "was not Ukrainian" and has called for his officials to have access to the site of the blast.

The preliminary findings came after Joe Biden and other western backers of Ukraine had thrown their weight behind the investigation, amid repeated assertions from Russia that it did not fire the missile.

The US President cast doubt on previous claims that the missile, which hit a grain silo in Przewodow and killed two farmers, was fired by Moscow.

OFM News