The Nato secretary general, Mark Rutte, has said the alliance is “ready to defend every inch” of its territory after a Russian drone hit an apartment building in Romania, a member state, during an overnight attack on neighbouring Ukraine.

The incident in Galați, which injured two people, prompted swift condemnation and the threat of repercussions.

Russia’s reckless behaviour is a danger to us all,” Rutte wrote on social media after a call with the Romanian president, Nicuşor Dan. “I affirmed that Nato stands ready to defend every inch of allied territory.”

On Friday Dan convened an emergency meeting of the country’s supreme council of national defence and the foreign ministry summoned Russia’s ambassador.

The foreign minister, Oana Țoiu, wrote on X: “We will officially communicate the consequences that this lack of responsibility on the part of the Russian Federation will have for the diplomatic relations between our countries, as well as the next steps at the European level regarding sanctions packages.”

The strike in Romania is the latest example of the war in Ukraine spilling beyond the country’s borders, amid growing concern over Russia’s wider campaign of hybrid warfare across Europe.