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OSLO (Reuters) - A knife attack in a supermarket in Oslo is being investigated as a possible act of terrorism, the head of the Norwegian police’s security service (PST) said on Friday.

A woman was knifed on Thursday as she was paying at the till and the suspect, a 20-year-old Russian man, was arrested soon after, police said.

“The man said under questioning that he wanted to kill several people and that this was an act of terror,” PST head Benedicte Bjoernland told a news conference.

The suspect had arrived in Oslo on Thursday, traveling from Russia via neighboring Sweden, she said. There were no other suspects.

Police were investigating possible links to Islamist extremism, Bjoernland said, adding that the victim was critically ill in hospital.

The most recent fatal terrorism attack in Norway was in 2011 when far-right militant Anders Behring Breivik killed 77 people in a bombing in central Oslo and a shooting spree on a nearby island.

In 2017, a 17-year-old Russian who prosecutors said had frequented Islamist websites was sentenced to nine months in jail for making a small bomb and bringing it to the center of Oslo on a busy Saturday night. The device failed to go off.