The presidents of the European Council and the European Commission have expressed alarm at the news of a blast having killed people on Polish territory and extended words of support for Poland.

“I am shocked by the news of a missile or other ammunition having killed people on Polish territory. My condolences to the families,” Charles Michel, the head of the European Council wrote on Twitter on Tuesday.

“We stand with Poland,” he wrote after reports of a blast close to the Polish-Ukrainian border which could have been linked to Russian missiles.

“I am in contact with Polish authorities, members of the European Council and other allies,” he said in a tweet.

Ursula von der Leyen, the European Commission president, wrote on Twitter: “Alarmed by reports of an explosion in Poland, following a massive Russian missile strike on Ukrainian cities.”

“I extend my condolences and my strongest message of support and solidarity with Poland and our Ukrainian friends,” von der Leyen added.

“We are closely monitoring the situation and are in touch with Polish authorities and partners and allies,” she also said.