The suspected gunman in an attack on a mosque in Norway on Saturday was inspired by recent white extremist attacks in New Zealand and the US, online posts suggest.

Police in Norway have so far only said the attack in Baerum, a town 20km from Oslo, the capital, will be investigated as a possible act of terrorism.

In messages posted on the day of the attack, Philip Manshaus, a 21-year-old man who has been named by local media as the main suspect, described himself as “chosen” by “Saint [Brenton] Tarrant”, the gunman who killed 51 people at mosques in New Zealand in March.

“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.

In a meme also posted by Manshaus, three rightwing extremists suspected of being responsible for other attacks this year are depicted and praised as heroes of the white nationalist movement.

Tarrant is described as having “addressed the Muslim problem” while Patrick Crusius, who has been charged with the attack in El Paso, Texas, in which 22 people died, is praised for “fighting to reclaim his country”.

A third attacker suspected of killing a woman during a Passover celebration at a synagogue in California in April is also praised, alongside antisemitic abuse.