Two Russian missiles have landed in NATO state Poland, killing two people and prompting a furious backlash from Ukraine's Volodymyr Zelensky and western heads of state as Russia denied the reports.
The rockets fell on a farm in Przewodow, a village in eastern Poland, close to the Ukraine border where they exploded around 3:40pm local time yesterday afternoon.
It is not yet known if the strike was intentional or not.
The Polish Foreign Ministry said a Russian produced rocket had hit a grain drying facility in the farm, and confirmed they had since summoned the Russian ambassador.
Three US officials speaking anonymously on Wednesday morning said that preliminary assessments suggested a missile could have been fired by Ukrainian forces at an incoming Russian projectile, resulting in the explosion.
The incident could have serious ramifications because of Poland's status as a NATO country, meaning it could opt to invoke NATO's Article 5 - which states an attack on one member state is treated as an attack on them all.
But reports suggest that the 30 member states will meet tomorrow morning as Article 4 may be activated instead, allowing NATO members to bring issues of concern to the bloc for discussion.
A press secretary for the Pentagon warned: "When it comes to our security commitments and Article 5, we have been crystal clear: we will defend every inch of NATO territory."
US President Joe Biden, who was woken up by his advisors to inform him of the attack, has called Polish President Andrzej Duda to express his "deep condolences" for the loss of life.
He later held an emergency meeting of G7 world leaders in Bali, and afterwards told reporters that "preliminary information" suggested the missile may not have been fired from Russia itself.
"I don't want to say that until we completely investigate, but it's unlikely in the minds of the trajectory that it was fired from Russia, but we'll see", he added.
Russia dismissed claims of an attack on Polish soil as a 'deliberate provocation' - but Ukraine said that it had warned of such an attack for a long time.
At 8pm GMT, government ministers in Poland gathered to discuss the incident and raised the readiness of parts of the country's army as they continued to investigate throughout the night.
Poland's Prime Minister, Mateusz Morawiecki, convened the Committee of the Council of Ministers for National Security and Defence Affairs "as a matter of urgency" this evening, government spokesman Piotr Müller confirmed.
Müller did not immediately confirm the reports of the US intelligence official and said the meeting was being held due to a 'crisis situation'.
He confirmed two people had been killed, and said Poland was looking into whether it could activate NATO Article 4 - an article that lets members bring any issue of concern to the table for discussion. This would trigger a meeting of all NATO members.
Reports since have suggested that Poland will trigger Article 4 and bring together NATO's member states for a meeting over the incident this morning.
Poland President Andrzej Duda also announced a further meeting of the National Security Council, which will be held at midday on Wednesday.
The two people who were killed were said to have died at the scene following the impact of the rockets, thought to have happened some time yesterday afternoon.
Initially, local fire services confirmed an explosion in the area but it later emerged that rockets had fallen there.
Both Russian missiles, according to Mirror sources, were S-300 weapons and Polish fighter jets were scrambled from Tomaszow-Lubelski airfield.
Images from the impact site of the rockets show burnt and twisted farm equipment, destroyed by the rockets and a huge crater in the ground. Another image shows a plume of smoke rising into the air after the attack.
Further pictures show had large bits of metal debris thrown across the area.
Reports suggest local residents heard two explosions when the rockets fell, and the area remains cordoned off as Polish authorities investigate.
Jens Stoltenberg, the General Secretary of NATO, said it was 'closely monitoring' the incident. He tweeted: "Spoke with President Duda about the explosion in Poland. I offered my condolences for the loss of life. NATO is monitoring the situation and Allies are closely consulting. Important that all facts are established."
The British Foreign Office were also 'urgently seeking clarity' like many countries who are scrambling to confirm all the facts before launching any action against Russia that could lead to the escalation of the war.
Prime Minister Rishi Sunak said: "I have just spoken with the Foreign Secretary and Defence Secretary. We are urgently looking into reports of a missile strike in Poland and will support our allies as they establish what has happened.
"We are also coordinating with our international partners, including NATO."
Politico reported that US officials believed the explosion wasn't caused by the remnants of a missile shot down by Ukraine armed forces, but rather a deliberate strike or an errant missile.
Following the deaths, Ukraine's Volodymyr Zelensky warned Russian terror would only continue to spread. In a video message this evening, he said: "Today, something that we have been warning for a long time has also happened. Terror is not limited to our state borders. Russian missiles hit Poland ... hit missiles on NATO territory.
"It's a matter of time before Russian terror goes further. The longer Russia feels impunity, the more threats there will be for anyone who is in range of Russian missiles."
One of Zelensky's advisors said the attack was a 'disguised mistake' and not an accident but a 'deliberately planned hello'.
Lord Richard Dannatt, former head of the British Army, told Sky News: "Modern technology is pretty accurate, so it's quite difficult to explain away that this might have been an accident.
"If it wasn't an accident then it was a test of the West's response, and that's something that's got to be thought through very carefully."
Latvia's Minister of Defence, Artis Pabriks expressed their condolences to Poland and blasted the Russian regime as 'criminal'.
Scenes from the on the ground this evening show a heavy presence of emergency services at the rural town as Poland continues its investigation.
The Estonian Foreign Ministry: "Latest news from Poland is most concerning. We are consulting closely with Poland and other Allies. Estonia is ready to defend every inch of NATO territory. We’re in full solidarity with our close ally Poland."
The Russian Defence Ministry denied reports of the attack and claimed it had nothing to do with them.
It said: "Statements by the Polish media and officials about the alleged fall of 'Russian' missiles in the area of the settlement of Przewodow is a deliberate provocation in order to escalate the situation.
"No strikes were made against targets near the Ukrainian-Polish state border by Russian means of destruction."
Neighbouring Moldova was also affected by more Russian strikes today after their bombardment of Ukraine knocked out power to much of the nation.
The Pentagon said it is looking into the reports around the explosion but could not currently corroborate them. Pentagon press secretary Brigadier General Pat Ryder reportedly said: "When it comes to our security commitments and Article 5, we have been crystal clear: we will defend every inch of NATO territory."
Lithuania's president echoed this message as well and Adrienne Watson, a spokesperson for the National Security Council, said on Twitter that the agency had seen reports out of Poland and was working with the Polish government to gather more information.
Poland plays a vital role in NATO supplies reaching Ukraine and Russia has warned in the past of its actions supporting Kyiv.
Russian ally Hungary have also convened a meeting of his country's defence council after the explosion in the eastern Polish village led to crude shipments on the Druzhba pipeline being suspended.
Germany, long criticised for not taking a hard enough line on Russia, spoke out on the attack as well. The country's foreign minister Annalena Baerbock said: "My thoughts are with Poland, our close ally and neighbor. We are monitoring the situation closely and are in contact with our Polish friends and NATO allies."
It is not known if the missiles were a purposeful strike or an unintended consequence of its missile strikes on Ukraine which included strikes on Lviv in western Ukraine, just 50 miles from the border.
But the action comes during the ongoing G20 summit where Putin's foreign minister Sergey Lavrov is present after Putin snubbed the meeting.
French president Emmanuel Macron said the G20 meeting would be an important moment to highlight what has happened in Poland.
Since the attack, Russian markets have responded and are significantly down and when confronted on the allegations over the deaths, Kremlin spokesperson told ITV News that: "Unfortunately I don’t have any information on that."
Today, Russia also pounded Ukraine's energy facilities with one of its biggest barrage of missiles yet, causing widespread blackouts.
They fired at least 90 missiles, estimated to be worth approaching half a billion dollars in total, in the shocking attack - one of the largest of its kind since the war began in February this year.
Zelensky said around ten million Ukrainians were left without power, including most of the city of Lviv and the entire Kharkiv region.
