Philip Manshaus, the 21-year-old identified as the man who allegedly opened fire at a Norway mosque Saturday (local time), injuring one, is claimed to have posted messages online on the day of the attack praising mass shooters.

The messages reportedly describe Manshaus as the "chosen" one of Brenton Tarrant , the man behind the fatal shooting of 51 at New Zealand mosques back in March, The Guardian reports .

"My time is up, I was chosen by Saint Tarrant after all… We can't let this continue, you gotta bump the race war threat in real life… it's been fun," one post reads.

One person has been injured in a shooting inside a mosque in Norway and a man has been apprehended, police say. (EPA)

Manshaus claims Tarrant's actions "addressed the Muslim problem". He also reportedly posted a meme celebrating other shooters as icons of the white nationalist movement.

Included was Patrick Crusius , charged over the fatal shooting of 22 in El, Paso Texas. Manshaus reportedly defends him for "fighting to reclaim his country".

The third individual featured in the meme was the man behind a fatal shooting at a California synagogue in April.

Earlier, Norway police representative Superintendent Rune Skjold told reporters the suspect, described only as a Norwegian man in his 20s, had praised figures like Vidkun Quisling, the leader of Norway under Nazi occupation during World War II, as well as sharing anti-immigrant stances.

The shooting is being investigated as a "possible act of terrorism", police said.

The victim was a 75-year-old member of the congregation, mosque director Irfan Mushtaq told TV2. (EPA)

The man is facing an attempted murder charge in the shooting at Al-Noor Islamic Center in Oslo. One person was injured in the incident, sustaining minor injuries, police said.

The suspect has also been charged with the murder of a woman found dead in his home.

The shooting at the mosque in an Oslo suburb occurred as Muslims around the world celebrate Eid al-Adha this weekend, one of the most important holidays of the Islamic calendar. It marks the height of the annual Hajj pilgrimage to Mecca in Saudi Arabia.

Norwegian police said earlier they were trying to determine whether there were wider threats to other mosques. Extra personnel were deployed Sunday to protect mosques and Eid celebrations.

Shortly after the attack, investigators found the body of a young woman at the suspect's home in Baerum, just west of Oslo.

A member of the mosque told Norwegian state broadcaster NRK that the shooting could have been much worse, but the suspect was stopped by a 75-year-old man.

The mosque earlier this year implemented extra security measures following the massacre of more than 50 people at two New Zealand mosques by a suspected right-wing extremist. (EPA)

Imran Mushtaq, a board member at the Al-Noor mosque, said more than a dozen people were praying inside the mosque just ten minutes before the suspect arrived. But by the time the shooting began, only three older men were left inside, said Mushtaq, who was at his home nearby at the time.

The suspect entered by shooting through the mosque's locked glass door, Mushtaq said. The 75-year-old managed to overpower the suspect, placed him in a chokehold and sat on top of him until police arrived. He suffered only minor injuries.