People gather to show support, outside the mosque Islamic Cultural Centre in Oslo. Picture: Fredrik Hagen /NTB scanpix via AP

Copenhagen, Denmark - A suspected gunman accused of an attempted terrorist attack on an Oslo mosque and separately killing his teenage stepsister "will use his right not to explain himself for now" in a detention hearing, his defense lawyer said Monday.

Unni Fries declined to comment on Norwegian media reports that the suspect was inspired by shootings in New Zealand, where a gunman killed 51 people in March, and on August 3 in El Paso, Texas, which left at least 22 dead.

Her client was arrested Saturday after he entered the Al-Noor Islamic Center in Baerum, an Oslo suburb. Police said the suspect was waving weapons but did not specify what type. One person was slightly injured before people inside the mosque held the suspect until police arrived on the scene.

Police then raided the suspect's nearby house and found the body of his 17-year-old stepsister.

Norway's Prime Minister Erna Solberg and Mohamed Rafiq background centre left, stand outside Thon Hotel in Baerum, Norway. Picture: Terje Pedersen /NTB scanpix via AP

The suspect has not been identified by officials but Norwegian media reported he was a 21-year-old Norwegian man named Philip Manshaus. Dagbladet, one of Norway largest newspapers, reported that on day of the attack, Manshaus wrote online he had been "chosen" by "Saint (Brenton) Tarrant", the Christchurch gunman.

The name of the Oslo mosque is similar to the one in the New Zealand attacks.

Prosecutors want him held on terror charges for four weeks.

Prime Minister Erna Solberg called the attempted attack a "direct attack on Norwegian Muslims."

The suspect's thwarted plans recall those of the Norwegian right-wing extremist who in 2011 killed 77 people in 2011. Anders Behring Breivik is serving a 21-year prison sentence for carrying out a terror attack.

AP