Polish Prime Minister Donald Tusk said an explosion that damaged a railway route linking Poland with Ukraine was an act of sabotage, as the country confronts rising hybrid threats from Russia. 

“The explosion was most possibly intended to blow up a train on the route,” Prime Minister Donald Tusk said in a video posted on X. 

On November 15, an explosive device destroyed a railway track close to the village of Mika, around 100 kilometers (62 miles) from the capital, Tusk said. Damage was also discovered elsewhere on the same rail route, he added.

Both acts occurred on the way between Warsaw and the Ukrainian border crossing in Dorohusk, used daily to carry passengers and western aid to Kyiv since the Russia’s full-scale invasion almost four years ago.

Tusk didn’t identify potential suspects for the incidents, which are currently being investigated. In the past, Poland has repeatedly blamed Moscow for an alleged increase in the number of cases of sabotage, including a fire that destroyed a shopping mall in Warsaw last year. The country is also grappling with the highest number of foreign cyberattacks in the European Union. 

The Polish army will inspect 120 kilometers of rail track leading to the Polish-Ukrainian border, the country’s Defence Minister Wladyslaw Kosiniak-Kamysz said in a post on X.

Recent months have also seen an increased number of attacks on the country’s water and sewage systems, Poland’s Deputy Prime Minister Krzysztof Gawkowski told Radio Zet on November 17 before Tusk’s post about possible sabotage.

In February, authorities arrested a Russian suspected of coordinating acts of sabotage against Poland, the U.S. and other allies by sending parcels containing camouflaged explosives and setting buildings ablaze.