NATO Secretary-General Jens Stoltenberg says the blast in eastern Poland, which killed two people, was probably caused by a Ukrainian air defence missile, but that Russia was ultimately responsible because it started the war in Ukraine.

His address followed an emergency meeting to respond to the explosion at a grain dryer near the Ukrainian border, which occurred while Russia was firing scores of missiles at cities across Ukraine.

Mr Soltenberg said one of NATO’s top priorities at the moment is to provide more air defence systems to Ukraine.

Polish President Andrzei Duda said earlier it was “highly probable” that the missile was fired by Ukrainian air defence.

“From the information that we and our allies have, it was an S-300 rocket made in the Soviet Union, an old rocket and there is no evidence that it was launched by the Russian side,”

“It is highly probable that it was fired by Ukrainian anti-aircraft defence.”

Earlier, US President Joe Biden had said the trajectories suggested the missile was unlikely to have been unleashed from Russia.

Ukrainian President Volodymyr Zelensky demurred, saying “I have no doubt that it was not our missile”, Ukrainian media reported.

He said he based his conclusion on reports from Ukraine’s military which he “cannot but trust”.

Britain remains cautious

“We are not going to rush to judgment. Our response will always be led by the facts,” British Foreign Secretary James Cleverly said in a speech to the British Parliament, Wednesday, adding the investigation into the incident would be led by Poland.

Mr Cleverly’s warning came after Mr Stoltenberg’s media briefing in Brussels, where he said “preliminary analysis suggests that the incident was likely caused by a Ukrainian air defence missile fired to defend Ukrainian territory against Russian cruise missile attacks.”

The foreign secretary condemned Vladimir Putin’s “brutal air campaign” on Ukraine on Tuesday, when waves of missiles hit cities across the country.

Tweet from @JamesCleverly

Ukraine claims evidence of  “Russian trace”

Ukraine wanted a joint study of Tuesday’s incident with its partners and to see the information that provided the basis for its allies.

Oleksiy Danilov, secretary of the National Security and Defence Council of Ukraine, said Ukraine wanted access to the site of the explosion. Kyiv was “completely open to a comprehensive study of the situation”, he wrote on the council’s official Facebook page on Wednesday.

Mr Danilov echoed Mr Zelensky in blaming Russia’s “missile terror”.

He provided no details of what evidence he was citing when he referred to a “Russian trace” behind the incident.

Asked whether Poland would grant Ukraine access to the site of the explosion and agree on a joint study, Polish Foreign Ministry spokesman Lukasz Jasina wrote by email: “We do not comment on this matter.”

-with AAP