CNN reported on Tuesday afternoon, about the same time that Russia unleashed its largest round of missile attacks against Ukrainian cities in more than a month, that a missile fell outside the small Polish settlement of Przewodow, some 6.4km west of the Ukrainian border.

Uncertainty surrounds the incident's circumstances, which represent the first direct hit on a NATO nation in the conflict's nearly nine-month duration. The missile's launcher and exact location are unknown, despite the Polish Foreign Ministry's claim that it was "Russian-made."

During the conflict, both Russian and Ukrainian troops have employed weapons developed in Russia, with Ukraine using Russian-built missiles as part of its air defense system.

US President Joe Biden told reporters after having an emergency meeting with G7 and NATO leaders outside the G20 conference that it was "unlikely" that the missile was launched from inside Russia, but he couldn't say for sure until the inquiry was complete.

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"We agreed to support Poland's explosion inquiry."

"And I'm going to make sure we find out exactly what happened," Biden said, adding that the leaders expressed condolences for the deaths of the two people.

"As we examine and move forward, we will decide together what to do next. The people gathered around the table were in complete agreement," he said.

A Nato military official told CNN after Biden's remarks that an alliance aircraft had been monitoring the missile when it was flying above Polish airspace at the time of the explosion.

The Nato military officer continued, "Intel with the radar tracks [of the missile] was delivered to Nato and Poland." The Nato official withheld information on the missile's launcher and point of origin.

According to a statement made by Dutch Prime Minister Mark Rutte online on Wednesday, the missile strike inside Poland's borders on Tuesday "would not have happened without Russia's horrendous missile attacks against Ukraine."

"To discuss the incident in Poland last night, the G7 and current NATO members met this morning in Bali during the G20. We all agree that the facts must be established first, and we thus support Poland's probe, commented Rutte.

Although it was unclear who launched the missile, Polish President Andrzej Duda indicated in earlier statements on Tuesday that the missile was "most likely" built in Russia. In a speech from the Bureau of National Security in Warsaw, Duda said, "We are working calmly and in a very peaceful manner.

According to a brief statement sent by the Russian Defense Ministry late Tuesday, the Kremlin has denied any role in the incident and described the Polish media reports that initially revealed the fatalities as "a planned provocation in order to aggravate the situation."

It further stated that "Russian weaponry have nothing to do with the wreckage images from the scene in the village of Przewodow that were published by Polish media."

The event in Poland is an attempt to spark a direct military confrontation between Nato and Russia, the Russian envoy to the UN said on Wednesday. The issue will be discussed at the UN Security Council meeting later in the day, the mission added.

Mateusz Morawiecki, the prime minister of Poland, stated on Tuesday that there is no indication of more missile strikes and that the missile strike in Przewodów appears to have been a "single act."

Morawiecki urged restraint, but he also declared that Poland would improve its military readiness and was considering using Article 4 of the Nato Treaty. Article 4 is a consultation procedure that enables members of the 30-nation alliance to present a problem for debate at the North Atlantic Council, which serves as its decision-making body. These problems are typically security related.

Whatever the findings of the Polish-led probe, the episode has confirmed long-standing worries about the possibility that a mistake on the battlefield may spark a Nato-Russian clash.

As the missile sailed above the village and the power of the explosion rocked surrounding windows, witnesses to the explosion recalled hearing a scary "whoosh" sound.

Local media displayed a picture of a crater and an overturned farm truck at the explosion scene. CNN is unable to independently verify the images.

In his speech, Duda announced that as part of a cooperative effort, the US would send experts to investigate the site.

Jens Stoltenberg, the secretary general of Nato, said it was crucial that "all facts are established" after speaking with Duda on Tuesday.

"I expressed my sympathy for the death. The Allies are closely collaborating, and Nato is keeping an eye on the situation. It is crucial that all facts are proven, according to Stoltenberg.

A sizable smoke cloud can be seen in the village's center in a resident's video that CNN geolocated and verified.