Calling itself the Army of Muhammad, the group, on Sunday, claims it has 5,000 fighters ready to resist the continuing US-led occupation.
Three members said the Army of Muhammad did not support the return of the former president Saddam Hussein.
"We want to make a new government, without Saddam but in the same style," one of the fighters told Newsweek.
The group began as a gathering of tribal Iraqi army veterans angry at the US-led occupation of their country.
"We met in small cells at first, far from the cities, in farms, and we started talking," said one of the fighters, identified as Kadhim Baghdadi, 34. "We took the decision that we must liberate the country."
The resistance fighters communicate daily with their central command through couriers bearing handwritten notes, the fighters added.
According to a statement read by one of the fighters, who identified himself as Muhammad al-Rawi, US forces have taken over Iraq under a false pretext, and without international authorization.
Al-Rawi also claimed occupation forces "kill our women and children and old men," and want to "bring the Jews to our holy land in order to control Iraq."
Four masked men identifying themselves as Army of Muhammad members appeared on Saturday in a videotape broadcast by Qatar's Aljazeera satellite news channel, warning they would turn Iraq "into a cemetery for the invaders and colonisers."
One of the men told Aljazeera that members of the former government would never participate in resisting the occupation since they had “handed over Baghdad to the enemies”.
The group said their resistance was legitimised by “international laws and traditions”.
A US military officials in Tikrit on Sunday said they were aware of the group, but added it was contemptible to invoke Islam's prophet in their fight.