WARSAW, Poland (AP) — Poland’s defence forces said an unknown object entered the country’s airspace Friday morning from the direction of Ukraine and then vanished off radars, and that all indications pointed to it being a Russian missile.

“Everything indicates that a Russian missile intruded in Poland’s airspace. It was monitored by us on radars and left the airspace. We have confirmation of this on radars and from allies” in NATO, said Poland’s armed forces chief, General Wiesław Kukuła.

Poland’s defence forces said the object penetrated about 40 kilometres (24 miles) into its airspace and left it after less than three minutes. The defence forces said both its radar and NATO radar confirmed that the object left Polish airspace.

Kukula said steps were being taken to verify those findings and eliminate the possibility of a technical error.

There was no comment from Russian officials.

NATO Secretary General Jens Stoltenberg said on X, formerly Twitter, that he had spoken with Poland’s president about the “missile incident” and said NATO was vigilant and monitoring the situation “as the facts are established.”

United States (US) National Security Advisor Jake Sullivan spoke with the head of Poland’s National Security Bureau, Jacek Siewiera, to express the “United States’ solidarity with Poland, our close NATO ally, as it deals with reports of a missile temporarily entering Polish airspace,” the White House said.

Sullivan pledged technical assistance to Poland and assured that US President Joe Biden was following the issue closely.

It was not immediately clear where the object disappeared from radar or in which direction it had been going. Troops were mobilised to identify and find it. There were no immediate reports of any explosion or casualties.

The governor of Lublin province in eastern Poland, Krzysztof Komorski, told the Onet news portal that the object appeared on radars near the town of Hrubieszow, where a border crossing with Ukraine is located. Komorski said he had no information to indicate it landed in Lublin province.

Poland’s border with Ukraine is also the European Union and NATO border with Ukraine.

Prime Minister Donald Tusk convened a meeting with the defence minister, military commanders and heads of national security bodies, followed by a meeting of the National Security Bureau with President Andrzej Duda, the supreme commander of Poland’s armed forces.

Duda said through an aide that there was “no threat at the moment” and nothing to suggest that ”anything bad” should be expected.

“The most important [thing] is that no one was hurt,” said the aide, Grazyna Ignaczak-Bandych.

On Friday, Ukrainian officials said Russia launched more than 100 missiles and dozens of drones against Ukrainian targets overnight in what an air force official called the biggest aerial barrage since Russia’s full-scale invasion of Ukraine in February 2022.

It was not clear whether the object that Poland reported was related to the barrage.

“As a result of such massive attacks, this can happen. The enemy is attacking our border territories, including in the west. This is another signal for our partners to strengthen the Ukrainian air defence,” Yurii Ihnat, spokesperson for Ukraine’s Air Force, said on national television about the incident.

Poland has been supporting Ukraine with military, humanitarian and political assistance.

This is not the first time an unauthorised object has entered Poland’s airspace from the direction of Ukraine since Russia’s full-scale invasion. In November 2022, two men were killed when a missile struck the village of Przewodow, a few kilometres from the border. Western officials said they believed a Ukrainian air defence missile went astray.