RUSSIA'S Defence Ministry said on Wednesday that an explosion in Polish territory on Tuesday had been caused by a Ukrainian air defence missile, and that Russian strikes in Ukraine had been no closer than 35 km (22 miles) from the Polish border.

"The photos published in the evening of Nov. 15 in Poland of the wreckage found in the village of Przewodow are unequivocally identified by Russian defence industry specialists as elements of an anti-aircraft guided missile of the S-300 air defence system of the Ukrainian air force," RIA news agency quoted the defence ministry as saying.

It was not possible to independently verify the images or the identification.

NATO member Poland's president said earlier that Warsaw had no concrete evidence to determine who fired a missile that struck a Polish grain facility some 6 km (4 miles) inside the border with Ukraine, killing two people.

A NATO source said U.S. President Joe Biden had informed Group of Seven and NATO partners that the blast in Poland had been caused by a Ukrainian air defence missile.