The suspect behind a weekend shooting in Oslo that left two dead and 21 wounded was remanded in custody for four weeks on Monday.

Zaniar Matapour will have no contact with the outside world until July 25, Oslo District Court ruled.

The 43-year-old is accused of killing two men and wounding 21 other people when he opened fire near a gay bar in central Oslo in the early hours of Saturday morning, amid celebrations linked to the city's Pride festival.

Norway's domestic intelligence service has described the attack as "an act of Islamist terrorism" and said Matapour had "difficulties with his mental health."

Norwegian police said they were still investigating Matapour's motive.

He has been charged with "terrorist acts", murder and attempted murder, but has so far refused to be interrogated by police.

According to his lawyer, he fears investigators will manipulate video recordings of his questioning.

A woman walks past the memorial at the site in Oslo, Norway where two people where shot in an attack against several gay bars
A woman walks past the memorial at the site in Oslo, Norway where two people where shot in an attack against several gay bars NTB via AFP / Beate Oma Dahle

Matapour, a Norwegian of Iranian origin, will undergo a preliminary psychiatric evaluation to help determine the state of his mental health and whether he can be held legally responsible for his actions.

He had been known to Norway's PST intelligence service since 2015, with concerns about his radicalisation and membership of "an extremist Islamist network".

Police said they were examining several possible theories, including an attack motivated by ideology, unstable mental health, a hate crime against the LGBTQ community, or a combination of factors.

The PST said it did not pick up on any "violent intent" when its services interviewed him last month.

Justice Minister Emilie Enger Mehl said there would be a review into the police and PST's handling of the case.

Nordic ministers visited the site of the attack on Monday, saying in a joint statement that they "stand together with the LGBTI community and against all forms of violence".

Oslo's Pride parade, which had been scheduled to take place for the first time in three years due to the Covid pandemic, has been postponed indefinitely.