A woman has been killed in an axe attack at the University of Warsaw in Poland, police said.

The university said she was a staff member and had come under attack in the main campus building on Wednesday evening. A university guard who came to her aid was seriously injured.

A 22-year-old Polish man has been arrested. His motives remain unclear although a local prosecutor said he was a third-year law student who was Polish but not from Warsaw.

The university described the attack as a "huge tragedy". It declared a day of mourning on Thursday with no classes taking place.

The attacker entered the college campus shortly after 18:40 local time (16:40 GMT).

From there he moved on to the university's biggest lecture hall, the Auditorium Maximum building.

Polish reports said the woman killed in the attack was a 53-year-old porter who died at the scene. The security guard who came to her help is 39.

The university said that everyone had been shocked by the murder.

"We express our great sorrow and sympathy to the family and loved ones," the rector, Alojzy Nowak, said in a statement.

Justice Minister Adam Bodnar was taking part in a panel discussion in a nearby lecture theatre. He said he had not seen the attack but was told by his state protection officers what had happened.

He praised one of his officers who he said ran to the scene to help the university guard who tackled the attacker.

Warsaw Mayor Rafal Trzaskowski also expressed his shock at what he described as a "macabre crime" on the campus. "This brutal attack must be severely punished," he added.

The university had been due to host its annual music festival, Juwenalia, on Friday and Saturday but that has also been cancelled. (BBC)

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