NATO member Poland and the head of the military alliance both said Wednesday that a missile strike in Polish farmland that killed two people did not appear to be intentional and was probably launched by air defenses in neighboring Ukraine. Russia had been bombarding Ukraine at the time in an attack that savaged its power grid.

“Ukraine’s defense was launching their missiles in various directions and it is highly probable that one of these missiles unfortunately fell on Polish territory,” said Polish President Andrzej Duda. “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 30-nation military alliance in Brussels, echoed the preliminary Polish findings.

Still, Stoltenberg and others laid overall but not specific blame on Russian President Vladimir Putin’s war.

“This is not Ukraine’s fault. Russia bears ultimate responsibility,” Stoltenberg said.

Secretary of Defense Lloyd Austin on Wednesday said the United States has "seen nothing that contradicts President Duda's preliminary assessment that this explosion was most likely the result of Ukrainian air defense missile that unfortunately landed in Poland," but stressed that while the investigation remains ongoing, "whatever the final conclusions may be, the world knows that Russia bears ultimate responsibility for this incident." 

Ukrainian President Volodymyr Zelenskyy disputed the preliminary findings and demanded evidence. He told reporters he had “no doubts” about a report he said he had personally received from his top commanders “that it wasn’t our missile or our missile strike.”

Ukrainian officials should have access to the site and take part in the investigation, he added.

“Let’s say openly, if, God forbid, some remnant (of Ukraine’s air-defenses killed a person, these people, then we need to apologize. We are honest people after all. But first there needs to be a probe, access — we want to get the data you have,” Zelenskyy said.

On Tuesday, Zelenskyy had called the strike “a very significant escalation.”

In response, Austin on Wednesday said the United States "will continue to stand in solidarity with the people of Ukraine as they defend their country," adding it is still early in the investigative process to make any definitive accusations. 

"We have full confidence in Poland's ability to to conduct this investigation in the proper way. And until that's complete, again, I think it'd be premature for anybody to jump to conclusions," Austin said. "I know that Ukraine has offered to participate and help in any way they can as well. So we won't get ahead of the investigation."

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, said he had unsuccesfully reached out to his Russian counterpart, Gen. Valery Gerasimov, amid the investigation, adding that U.S. officials will likely have confirmed data on the source of the missiles that landed in Poland "very shortly."

The initial assessments of Tuesday’s deadly landing of the Soviet-era missile appeared to dial back the likelihood of the strike triggering another major escalation in the nearly 9-month-old Russian invasion of Ukraine. If Russia had deliberately targeted Poland, that could have risked drawing NATO into the conflict.

The missile came down Tuesday near Poland’s border with Ukraine. Three U.S. officials said preliminary assessments suggested it was fired by Ukrainian forces at an incoming Russian one. The officials spoke on condition of anonymity because they weren’t authorized to discuss the matter publicly.

Before the Polish and NATO assessments, U.S. President Joe Biden had said it was “unlikely” that Russia fired the missile but added: “I’m going to make sure we find out exactly what happened.”

That assessment and Biden’s comments at the Group of 20 summit in Indonesia contradicted information earlier Tuesday from a senior U.S. intelligence official who told The Associated Press that Russian missiles crossed into Poland.

Former Soviet-bloc country Ukraine maintains stocks of Soviet- and Russian-made weaponry, including air-defense missiles, and has also seized many more Russian weapons while beating back the Kremlin’s invasion forces.

Ukrainian air defenses worked furiously against the Russian assault Tuesday on power generation and transmission facilities, including in Ukraine’s western region that borders Poland. Ukraine’s military said 77 of the more than 90 missiles fired were brought down, along with 11 drones.

The Kremlin on Wednesday denounced Poland’s and other countries’ initial reaction to the missile incident and, in rare praise for a U.S. leader, hailed the response of the U.S.

“We have witnessed another hysterical, frenzied, Russophobic reaction that was not based on any real data,” Kremlin spokesman Dmitry Peskov told reporters on Wednesday. He added that “immediately, all experts realized that it could not have been a missile linked to the Russian armed forces,” and pointed to a “restrained, much more professional reaction” of the U.S. and its president, Joe Biden.

In Brussels, NATO countries were coming together Wednesday for emergency talks. There was no immediate proof that Tuesday’s blast was a deliberate, hostile attack on NATO member Poland that could trigger the alliance’s provisions for a collective military response.

Russia denied any involvement. But Ukraine was under countrywide Russian bombardment Tuesday by barrages of cruise missiles and exploding drones, which clouded the picture of what exactly happened in Poland and why.

In Europe, NATO members Germany and the U.K. were among those stressing the need for a full investigation. German Chancellor Olaf Scholz warned against jumping to conclusions “in such a serious matter.”

Still, Scholz and others also laid overall but not specific blame on Russian President Vladimir Putin’s invasion of Ukraine.

“This wouldn’t have happened without the Russian war against Ukraine, without the missiles that are now being fired at Ukrainian infrastructure intensively and on a large scale,” Scholz said.

U.K. Prime Minister Rishi Sunak echoed that assessment, saying: “This is the cruel and unrelenting reality of Putin’s war.”

Ukrainian President Volodymyr Zelenskyy called it “a very significant escalation.” On the other end of the spectrum, China was among those calling for calm and restraint.

Former Soviet-bloc country Ukraine maintains stocks of Soviet- and Russian-made weaponry, including air-defense missiles, and has also seized many more Russian weapons while beating back the Kremlin’s invasion forces.

Damage from the aerial assault in Ukraine was extensive and swaths of the country were plunged into darkness. Zelenskyy said about 10 million people lost power but tweeted overnight that 8 million were subsequently reconnected, with repair crews laboring through the night. Previous Russian strikes had already destroyed an estimated 40% of the country’s energy infrastructure.

NATO Secretary-General Jens Stoltenberg called the meeting in Brussels of the alliance’s envoys. The U.N. Security Council also planned to meet Wednesday for a previously scheduled briefing on the situation in Ukraine.

If Russia had deliberately targeted Poland, it would risk drawing NATO into the conflict.

Polish media reported that the strike took place in an area where grain was drying in Przewodow, a village near the border with Ukraine.

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.

The Russian bombardment also affected neighboring Moldova. It reported massive power outages after the strikes in Ukraine disconnected a power line to the small nation.

The assault killed at least one person in a residential building in Ukraine’s capital, Kyiv. It followed days of euphoria in Ukraine sparked by one of its biggest military successes — the retaking last week of the southern city of Kherson.

With its battlefield losses mounting, Russia has increasingly resorted to targeting Ukraine’s power grid, seemingly hoping to turn the approach of winter into a weapon by leaving people in the cold and dark.