Russia on Wednesday accused Ukraine of a deadly blast in Poland, with Belgium saying it was likely caused by Kiev’s air defenses firing at Moscow’s incoming missiles.

The blast at an agricultural building on Tuesday killed two people, left the village of Przewodow in shock and sparked international concern that the conflict could escalate further.

Ambassadors from members of the NATO military alliance headed to Brussels for emergency talks after Poland put its military on high alert after the blast and summoned the Russian ambassador.

“Based on the preliminary information available, the attacks are most likely the result of Ukrainian anti-aircraft systems deployed to knock out Russian missiles,” Belgian Defense Minister Ludivine Dedonder said in a statement.

US President Joe Biden had said it was “unlikely” that the missile came from Russia, and the Kremlin said it had “nothing to do with it”.

“Photos of the wreckage … have been positively identified by Russian military experts as fragments of a guided anti-aircraft missile from a Ukrainian S-300 air defense system,” Russia’s Defense Ministry said in a statement.

It added that “attacks on targets were carried out only on the territory of Ukraine and at a distance of not less than 35 kilometers from the Ukrainian-Polish border”.

But Ukraine’s Foreign Minister Dmytro Kuleba previously dismissed the idea that it could have been a Ukrainian missile as a “conspiracy theory”.

The impact occurred at 1440 GMT on Tuesday in the village of Przewodow, killing two farm workers.

Police cordoned off the blast site and sirens wailed in the distance.

“I’m afraid. I didn’t sleep all night,” said Anna Magus, a 60-year-old teacher at the local elementary school.

“I hope it was a stray missile, otherwise we are helpless,” she said.

In Bali, Indonesia, Western leaders warned against jumping to any conclusions.

China said “all relevant parties should remain calm and exercise restraint to avoid escalation,” while Chancellor Olaf Scholz called for a “careful investigation” and warned against “rash” judgments.

According to a copy of his speech seen by AFP, Ukrainian President Volodymyr Zelenskyy said the missile incident was “a true declaration by Russia for the G20 summit”.

Polish Deputy Foreign Minister Pawel Jablonski also called for caution, but told RMF radio that “in all probability we are dealing with a consequence of the Russian actions”.

He also responded to criticism of Poland’s defence.

“Anti-missile defense systems around the world are never 100% effective systems, protecting every millimeter of every country’s territory,” he said.

Poland held an emergency National Security Council meeting on Tuesday and summoned Moscow’s ambassador to the incident to make “immediate detailed statements”.

The government also said it had increased “the state of readiness of some combat units and other uniformed services.”

Russia invaded Ukraine on February 24 and still holds parts of Ukrainian territory despite a series of battlefield defeats in recent months.

Poland – which shares a 530-kilometer border with Ukraine – has taken a leadership role in the region, providing military and humanitarian aid to its eastern neighbor and sanctioning Russia.

The conflict has caused deep concern in Poland, where memories of Soviet dominance remain unvarnished.

Poland is protected by NATO’s commitment to collective defense – enshrined in Article 5 of its founding treaty – but the Alliance’s response is likely to be heavily influenced by whether the incident was accidental or premeditated.

Warsaw has said it can invoke Article 4 of the treaty, which allows any member to convene urgent talks if it believes its “territorial integrity, political independence or security” is at risk.

Zelenskyy called the missile incident “a very significant escalation,” while the Russian Defense Ministry dismissed reports that it was blamed as a “provocation” to escalate tensions.

“The incident of Ukraine’s alleged ‘missile attack’ on a Polish farm proves only one thing: the West is moving closer to world war with a hybrid war against Russia,” Dmitry Medvedev, deputy chairman of the Russian Security Council, said on Twitter.

The blast came after Russian missiles hit cities across Ukraine on Tuesday, including Lviv near the border with Poland.

Zelensky said the strikes cut power to about 10 million people, although later restored to eight million of them, and also triggered automatic shutdowns at two nuclear power plants.

He said Russia fired 85 rockets at energy facilities across the country and condemned the attacks as an “act of genocide” and a “cynical slap in the face” by the G20.

Moldova, which also borders Ukraine, reported power outages over rockets fired at its neighbors and urged Moscow to “stop the destruction now.”