WARSAW—Polish Prime Minister Donald Tusk described an explosion on the country’s rail network near the Ukraine border as an “unprecedented act of sabotage,” casting it among a string of suspected attacks targeting European infrastructure in recent months.

Evidence suggests the Russian secret services appears to have ordered the blowing up of a railway line in Poland over the weekend, a government spokesman said on Tuesday.

"Russia is accused of all manifestations of the hybrid and direct war that is taking place," Kremlin spokesman Dmitry Peskov told a Russian state television reporter.