A 37-year-old caretaker has died after being stabbed by a former pupil at a school in Poland, police have said.

The 15-year-old entered the primary school in Leszczydół-Nowiny, north of Warsaw, at around 09:00 (07:00 GMT) and attacked the caretaker, before being overpowered by a teacher and the school’s headteacher who were also injured.

Prime Minister Donald Tusk said the boy was wearing a helmet to which a camera was attached, and appeared to have been “intending to film the knife attack”.

It comes after a 19-year-old was arrested on suspicion of a stabbing attack at another school in which nine people were injured on Wednesday, and officials said they had prevented a third such attack the same day.

Interior Minister Marcin Kierwiński said a 17-year-old was detained in the town of Sierpc, north-west of Warsaw, after stating “on school grounds that he planned to do something… dangerous – that he intended to harm someone”.

Teachers had alerted the police, who found that the teenager was in possession of two knives.

“The young person had been searching for information on how to orchestrate a ‘bloody’ event of this kind,” Kierwiński said.

Tusk said he feared a “grim copycat phenomenon” at an emergency meeting to discuss the incidents on Thursday, and ordered police to visit schools daily to prevent more violence.

The 15-year-old who attacked the caretaker on Thursday was carrying three knives, Poland’s interior ministry spokesperson Karolina Galecka said.

Polish media report that the caretaker had tried to stop him from entering the school.

The boy used to study at the John-Paul II primary school, but his motives for the attack are unclear, Galecka added.

The teacher and the headteacher’s lives are not in danger, the ministry’s spokesperson said.

Local media, citing a police spokesperson, reported authorities had information to suggest incidents over the past two days could be related to an internet challenge.