Several Polish retail chains, including Biedronka and children’s retailer Smyk, withdrew Halloween items such as fake or plastic knives and some costumes after recent stabbing incidents at schools. The companies said such products were inappropriate under the circumstances and could create undesirable associations.

The latest incident, on Saturday, involved a 21-year-old woman who injured three people at an educational institution. Authorities said the recent attacks were not linked to an organised group. About 20,000 police officers were deployed to schools on Monday amid online rumours of a “Blood Friday”; Prime Minister Donald Tusk said the deployment had helped bring the situation under control. The government is seeking to speed up legislation to make it easier to remove harmful online content.