WARSAW — Saboteurs who damaged a small section of a rail line linking the Polish capital to the eastern city of Lublin and on to Ukraine were two Ukrainians working for Russia, Prime Minister Donald Tusk told the Polish parliament Tuesday.

Train traffic along the busy route was halted Sunday morning after a high-speed Intercity train driver spotted damage to the line, warning nearby trains. “The outcome could have been a serious disaster with victims,” Tusk told MPs.

The perpetrators are two Ukrainian nationals “who have been operating and cooperating with Russian services for a prolonged period of time,” the Polish leader said. They had left their country for Belarus, from where they arrived in Poland shortly before carrying out the attack on the rail line. Both returned to Belarus before Polish services identified them. 

Tusk said one of the suspects had a track record of being involved in acts of sabotage in Ukraine. The other, he added, was a resident of the eastern Ukrainian region of Donbas.

“Polish security services and prosecutors have all personal data of these individuals, as well as recorded images of them,” Tusk said, adding Poland will ask Belarusian and Russian authorities to hand over the suspects to face trial.

The Warsaw-Lublin train route that was attacked is one of country’s busiest, linking the capital to the biggest city in eastern Poland and on toward Ukraine. 

Tusk described the two attempts at sabotaging the line. “The first involved placing a steel clamp on the track, with a likely intention to derail a train. The incident was meant to be recorded by a mobile phone with a power bank that had been set up near the tracks. That attempt proved entirely unsuccessful.

“[In] the second incident … a military-grade C-4 explosive was detonated using an initiating device connected by a 300-meter electrical cable.”

Tusk also said that the government will introduce a higher degree of security alert, known as “Charlie,” along selected rail lines. A lower security alert, “Bravo,” remains in place for the rest of the country.

Since Russia’s full-scale assault on Ukraine in February 2022, Poland has been on high alert for cases of foreign espionage and sabotage, and has arrested multiple people on those grounds.

Last month, two Ukrainian nationals were detained on suspicion of spying for a foreign intelligence service. Other recent incidents include an alleged Belarusian refugee accused by authorities of being a Russian operative, a fire set in a shopping mall near Warsaw and an alleged attempt to sabotage a railway station in southern Poland by leaving an unmarked railcar on tracks used by passenger trains.

“The adversary has begun preparations for war,” the Polish chief of the general staff, Gen. Wiesław Kukuła, told Polish Radio Monday.

“It is building a certain environment here that is intended to undermine public trust in the government and institutions such as the armed forces and the police. This is to create conditions conducive to potential aggression on Polish territory,” Kukuła said.