Three violent attacks at Polish schools this week were driven by the "glorification of violence" online, Prime Minister Donald Tusk said.
The incidents have left one woman dead, a caretaker killed, and several students and teachers wounded.
Tusk explained that "these are very often spontaneous actions inspired by online activity" during a crisis meeting with security services. He said the attacks are "nihilistic violence" associated with the extreme right.
Polish police have arrested 117 suspects across the country for weapons possession, or for threatening to attack schools. They have also searched tens of thousands of schools for potential threats.
An armed woman was arrested on Saturday after injuring three people while attacking a 17‑year‑old girl in Warsaw’s educational institution, as reported by media.
The day after two earlier stabbings, the caretaker of a primary school in Leszczydol-Nowiny was killed by a 15‑year‑old student, events that prompted nationwide police visits to reassure pupils.
Security services also met after receiving information about a potential threat to Tusk and Defence Minister Wladyslaw Kosiniak‑Kamysz, treating the threat as "deadly serious."
