The suspect detained by police after the attack that left three adults and five teenagers injured. (AFP pic)

WARSAW: Officers have arrested a 19-year-old man after seven people were wounded in a knife attack at a high school in Poland, police said Wednesday.

The attack happened at a school in Ostroleka, 20 kilometres (12 miles) north of the capital Warsaw, said police, who released a blurred photo of the suspect following his arrest.

Ostroleka prosecutor Elzbieta Lukasiewicz said the victims were students and teachers.

"It appears that the boy went into the school and attacked the students and teachers with a dangerous tool," Lukasiewicz told news channel TVN24.