A Facebook page belonging to an Auckland man shows pictures of him posing with an Islamic State flag, holding an AK47-style rifle and speaking of his role in a holy war.

Police said Harun Abdul-Majeed SaifuAllah's profile was a "security matter" and have refused to comment. However, it is understood they are investigating Mr SaifuAllah following inquiries by the Herald.

Mr SaifuAllah, 23, told the New Zealand Herald that he "100 per cent" supported the views and actions of Islamic State.

He said he changed his name three years ago but was born as William Ringo Ratapu-Howard in South Auckland, where he still lives.

He said the Government had confiscated his passport last year, stopped him travelling to Sydney in May where he planned to marry his Lebanese fiancée and that he had repeatedly been questioned by the SIS about his beliefs.

Mr SaifuAllah has multiple photos and comments on his Facebook page professing allegiance to the terrorist group.

In a 2014 interview with TVNZ, he said he did not support the views of the terror organisation. He does now.

"These are my views and I support them 100 percent," he said.