A woman has been arrested after injuring three people in the third knife attack recorded at schools in Poland this week.

Axar.az reports, citing BBC, that the 21-year-old used a "dangerous object" to attack a 17-year-old girl at an educational institution in the capital Warsaw, police have told news agencies PAP and AP.

It comes a day after thousands of police visited schools across Poland following two stabbing attacks earlier in the week, one of which killed a female caretaker.

A Warsaw police spokesperson said they could not confirm whether the latest incident was related to the two previous attacks.

Authorities told local media that the 17-year-old injured on Saturday had been taken to hospital, but her condition is not life-threatening. Two other women aged 17 and 24, who had come to submit enrolment documents were also injured, the state news agency reported.

Police told local media that the suspected attacker was a student at the school and initial findings suggest she did not know the three victims.

Schools in Poland had been stepping up security following knife attacks at schools across the country on 7 and 8 October. Polish police said they had arrested 76 people after deploying to schools across the country.

"When it comes to the safety of Polish children and peace in our schools, there is no room for compromise," Polish Prime Minister Donald Tusk said ahead of the operation.