Poland's president has said a missile blast that killed two people near its border with Ukraine appears to have been an "unfortunate accident" and not an "intentional attack".
But ultimately responsibility lies with Russia, which launched a barrage of missile attacks on Ukraine on Tuesday, Andrzej Duda said.
It was highly probable that the rocket, which was Russian-made, was used by the Ukrainian air defence.
He continued: "From the information that we and our allies have, it was an S-300 rocket made in the Soviet Union, an old rocket and there is no evidence that it was launched by the Russian side. It is highly probable that it was fired by the Ukrainian anti-aircraft defence."
The missile landed outside the rural Polish village of Przewodow, about four miles west of the Ukrainian border on Tuesday afternoon, killing two people.
It came just hours after Russia launched a huge barrage of strikes on cities across Ukraine, plunging around 10 million people into darkness without power. Ukraine’s military said 77 of the more than 90 missiles fired were brought down, along with 11 drones.
It marked the first time a NATO country has been directly hit during the almost nine-month conflict.
Duda said “it was not an attack on Poland,” but added that Tuesday’s incident was a missile used for anti-missile defence, meaning it was used by Ukraine’s defence forces.
Jens Stoltenberg, Secretary General of NATO, said the Polish missile incident demonstrates that the war in Ukraine “which is President Vladimir Putin’s responsibility – continues to create dangerous situations”.
He continued: "[The missile was] likely caused by Ukraine but not Ukraine’s fault. Let me be clear, this is not Ukraine’s fault. Russia bears ultimate responsibility as it continues its illegal war against Ukraine."
“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", he said.
If Russia had deliberately targeted Poland, it would risk drawing NATO into the conflict.
Russia’s Defense Ministry denied being behind “any strikes on targets near the Ukrainian-Polish border” and said in a statement that photos of purported damage “have nothing to do” with Russian weapons.
As a former Soviet-bloc country, Ukraine holds stocks of Soviet and Russian-made weaponry, including air-defence missiles.
The Kremlin has accused some western countries, especially Poland, of reacting “hysterically” to the missile strike, but said in a rare show of praise that President Biden had shown restraint.
Margarita Simonyan, editor-in-chief of state news channel Russia Today, baselessly suggested that the UK could have played a role.
She said: “This is either a Ukrainian mistake or a Polish provocation. Or British."
Germany said on Wednesday it could send its own warplanes to support patrols over Poland.
