In what Prime Minister Donald Tusk called an “unprecedented act of sabotage," a segment of a rail line linking Poland's capital, Warsaw, to the border with Ukraine was blown up over the weekend. Another segment further south was also damaged in what officials say was likely sabotage as well.

Prime Minister Donald Tusk said the explosion and another attempted act of sabotage over the weekend were a major escalation by Moscow.

Poland's Prime Minister Donald Tusk said Monday that an explosion on a section of railway line used for deliveries to Ukraine was an "unprecedented act of sabotage."