NATO said there was no indication that the missile strike that hit a Polish border village on Tuesday night was deliberate, saying that Russia was ultimately to blame as it continues to bombard Ukraine with missiles.
The military alliance's secretary-general, Jens Stoltenberg, said the missile incident took place "as Russia launched a massive wave of rocket attacks across Ukraine."
While the investigation was ongoing into the incident, he said, "there was no indication this was the result of a deliberate attack" and no indication it was a result of "offensive military actions against NATO."
Preliminary analysis, as previously reported, suggests the incident was caused by a Ukrainian air defense missile fired to "defend Ukrainian territory against Russian cruise missile attacks."
"But let me be clear, this is not Ukraine's fault. Russia bears ultimate responsibility as it continues its illegal war against Ukraine," he said.
The comments come after the alliance's North Atlantic Council held an emergency meeting following the missile strike that hit Poland on Tuesday night, killing two civilians.
Early Wednesday morning, The Associated Press reported, citing three unnamed U.S. officials, that preliminary assessments indicated "the missile that struck Poland had been fired by Ukrainian forces at an incoming Russian missile."
Other media agencies, including NBC News, cited similar details on Wednesday; Reuters reported a NATO source as saying President Joe Biden had told the G-7 and NATO partners that the strike was caused by "a Ukrainian air defense missile," while The Wall Street Journal cited two senior Western officials briefed on the preliminary U.S. assessments as saying the missile was from a Ukrainian air defense system.
Those assessments came after Biden said Tuesday that it was "unlikely" the missile was fired from Russia, citing the trajectory of the rocket. President Andrzej Duda of Poland said Wednesday that there was no indication that this was an intentional attack on Poland.
"There are many indications that it was an air defense missile, which unfortunately fell on Polish territory," Duda said.
Ukraine's Defense Ministry responded cautiously to reports suggesting its own armed forces fired the missile that hit Poland, saying it wanted to see the evidence that NATO's assessment was based upon.
Yuriy Sak, an advisor to Ukraine's defense minister Oleksiy Reznikov, told CNBC earlier Wednesday that Kyiv welcomed a thorough investigation of the incident, but said the issue was "very sensitive."
"It is too early to give any definitive answers and it's very dangerous to jump to any conclusions," Sak said before NATO's press briefing.
"Before any conclusions are made, an investigation must be done. So, that is where we stand," he said.
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After NATO's comments, Oleksiy Danilov, head of Ukraine's National Security and Defense Council, tweeted that Kyiv favored a "joint study" into the incident, and wanted to see the evidence held by its allies that suggested it was involved.
Danilov said on Twitter that Ukraine was "ready to hand over the evidence of the Russian trail that we have" but Kyiv was still awaiting "information from our partners, on the basis of which a conclusion was made that it is a Ukrainian air defense missile."