A 65-year-old Muslim worshipper is being hailed a hero after he managed to overpower a gunman in a suspected terror attack at a mosque in Norway.

Police say the suspected shooter at the al-Noor Islamic Centre near Oslo was a young, white man carrying several guns who had shared far-right, anti-immigrant views online.

“We’re investigating this as an attempt at carrying out an act of terrorism,” assistant chief of police Rune Skjold told a news conference on Sunday.

The suspected gunman was held down by worshippers inside the mosque before police arrested him after Saturday’s attack, police said.

“These people showed great courage,” Skjold said.

In a spectacular display of bravery during the attempted terror attack, in which shots were fired but no one was hit, 65-year-old worshipper Mohammad Rafiq was the first to tackle the shooter and pin him down while police arrived.

The retired Pakistani Air Force officer was one of only three people inside the mosque at the time of the attack, preparing for Sunday’s celebration of the Eid-al-Adha festival, mosque spokesman Waheed Ahmed told Reuters.

This is Muhammad Rafiq. Know his name.

Yesterday, when a white supremacist terrorist tried to carry out Christchurch-style massacre in a Norway Mosque, this 75 year old jumped on him, held him in a chokehold & sat on him till police arrived.

You don’t mess with desi uncles! pic.twitter.com/LauKW6UWAk

— Kashif Chaudhry (@KashifMD) August 11, 2019

Aided by an interpreter, Mr Rafiq told Reuters he “suddenly heard shooting from outside” before a man entered the building with guns and pistols.

“He started to fire towards the two other men,” Mr Rafiq said, describing how he then grabbed the attacker by holding him down and wrestling the weapons off him.

His eye red and one hand swollen, Mr Rafiq, who has lived in Norway for the past two and a half years, said he was still recovering from the attack.

“He put his finger inside my eye, up to here; full finger inside my eye,” he said.

The attacker, who has not been named, was also suspected of killing his own sister, who was found dead at his home, police said earlier.

Worshippers from the Al-Noor mosque in Baerum arrive at the Thon hotel to attend the prayer during the first day of Eid al-Adha. Photo: AFP/Getty

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

Norwegian Prime Minister Erna Solberg said police had ramped up security on Sunday as thousands of Muslims gathered at mosques for the Eid celebration.

While the government continuously tries to combat hate speech, more must still be done, she added.

“We are trying to combat this, but it’s a challenge. I think it’s a world-wide challenge in a sense,” Solberg said.

In 2011, anti-Muslim neo-Nazi Anders Behring Breivik massacred 77 people in Norway’s worst peacetime atrocity, the majority of them teenagers at a youth camp.

-with AAP