“I reiterated the UK’s solidarity with Poland and expressed condolences for the victims,” Sunak said on Twitter. “We will remain in close contact and continue to coordinate with our Nato allies.”

A readout of the call issued by his Downing Street office also said that Duda had updated Sunak on the Polish investigation efforts, with Sunak offering “any assistance needed to urgently establish what happened.”

Two people were killed in an explosion in Przewodow, a village in eastern Poland about 6km from the border with Ukraine, firefighters said. Media reports said the strike hit a grain-drying facility.

The Associated Press earlier cited a senior US intelligence official as saying the blast was caused by Russian missiles crossing into Poland.
Nato allies said they were investigating the incident, while Russia’s defence ministry denied the reports and described them as “a deliberate provocation aimed at escalating the situation.”

Foreign minister James Cleverly had said earlier that the UK was urgently looking into the reports, adding they were in contact with Poland and Nato allies.

The reports come after Russia was pounding cities across Ukraine with missiles on Tuesday, in attacks that Kyiv said were the heaviest wave of missile strikes in nearly nine months of war.

Some hit Lviv, which is less than 80km from the border with Poland.