Polish Prime Minister Donald Tusk has said an object that crashed into a field in eastern Poland in the early hours of Thursday was probably a Russian missile.

The unidentified object caused a 10m-wide (33ft) crater a short distance from the village of Tarnawa Kolonia, about 100km (62 miles) from the border with Ukraine, during a Russian attack on the city of Lviv.

"All the indications are that it was a Russian Kh-101 ballistic missile, but we want to be 100% certain about the type of missile and who launched it," Tusk said during a specially convened meeting in nearby Lublin.

Ukraine's acting Foreign Minister Andriy Sybiha said earlier on Thursday that a Russian Kh-101 cruise missile had "crossed into Poland as part of Russia's massive strike against Ukraine, violating Nato airspace".

Tusk said he was in contact with fellow European leaders before heading to the scene of Thursday's incident.

There were no reports of casualties in Thursday's incident, he said, but it was being treated as serious. There was no immediate threat as it had not landed in a built-up area, Tusk added: "We were prepared to shoot it down if had continued its flight."

A number of Russian drones and one unarmed Russian missile have landed in Poland since Russia's full-scale war in Ukraine began in February 2022.

Two Polish farmers were killed by a missile that landed just over the border from Ukraine in November 2022, but that was believed to have been a Ukrainian air defence missile responding to a Russian attack.

Defence Minister Wladyslaw Kosiniak-Kamysz said about 20 objects were seen close to Polish airspace overnight and pyrotechnical analysis was being carried out to determine the identity of the object that fell near Tarnawa Kolonia.

Poland's military detected the object at about 03:40 on Thursday (01:40 GMT) and sent an F-16 fighter jet to intercept it before it disappeared minutes later from radar systems. A military helicopter was then sent to search the area.

Air raid sirens blared in Lublin and Krasnystaw further to the south-east because of the Russian airstrikes that killed eight people in neighbouring Ukraine. Residents in Tarnawa Kolonia reported hearing a loud bang at about 04:00 and police found the crash site about an hour later.

The Polish leader had met Ukrainian President Volodymyr Zelensky in Lublin the previous evening as Zelensky was returning from talks with US President Donald Trump.