A man has been arrested after seven people were injured in an attack at a school in Poland.

Police said a 19-year-old student was arrested following the incident in the northeastern city of Ostroleka, north of Warsaw.

A "sharp object" was used in the attack, which happened at around 11am local time on Wednesday, police said.

The injured included students and teachers at the school, reported the Associated Press.

Two of them were reported to be in a serious condition.

Police said five of the victims were aged under 18.

The alleged attacker was hurt at the time of his arrest, police said, but no more details about his condition have been released.

The injured were being treated at a hospital in Ostroleka, TVN24 reported.

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The mayor of Ostroleka confirmed an attack had taken place and several people had been hurt.

Pawel Niewiadomski added: "The most important information is that the situation has been brought under control."