Prezewodow: The missile blast in Poland that killed two people was mostly likely an unfortunate accident, not an “intentional attack”, Poland’s president said on Wednesday.

President Andrzej Duda said that neighbour Ukraine likely launched the Soviet-era projectile as it fended off a Russian air assault that savaged its power grid, but he also said that the ultimate responsibility lies with Russia.

“Ukraine’s defence was launching their missiles in various directions and it is highly probable that one of these missiles unfortunately fell on Polish territory,” Duda said.

“There is nothing, absolutely nothing to suggest that it was an intentional attack on Poland.”

NATO Secretary-General Jens Stoltenberg, at a meeting of the military alliance in Brussels, agreed with the assessment.

“An investigation into this incident is ongoing and we need to await its outcome. But we have no indication that this was the result of a deliberate attack,” Stoltenberg told reporters.

The country’s prime minister, Mateusz Morawiecki, said on Wednesday that Poland was still analysing the possibility of launching the NATO Article 4 procedure, but it seemed it might not be necessary to use that measure.

US President Joe Biden and other Western backers of Ukraine threw their weight on Wednesday behind an investigation into why and how a missile that Poland said was Russian-made came down in Polish farmland, killing two people, when Russia was savaging the Ukrainian power grid with missiles and exploding drones.

Biden said it was “unlikely” that Russia fired the missile but added, “we’ll see,” and vowed: “I’m going to make sure we find out exactly what happened.”