"The al-Qaeda Organisation in the Land of Two Rivers (Iraq) is declaring all-out war on the Rafidha (a pejorative term for Shia), wherever they are in Iraq," said the voice which could not be immediately verified but sounded like previous recordings attributed to al-Zarqawi.
"As for the government, servants of the crusaders headed by Ibrahim al-Jaafari, they have declared a war on Sunnis in Tal Afar," the clip added.
Earlier on Wednesday, al-Qaida said in an internet posting it was waging a nationwide suicide bombing campaign to avenge the military offensive on Tal Afar as a string of explosions in Baghdad killed at least 150 people.
Warning to others
The purported al-Zarqawi recording also warned all other religious and tribal groups to join his anti-government campaign or also face attacks, saying: "You must choose between the good side and the bad side.
"Any religious group that wants to be safe from the blows of the mujahidin must [disavow] the government of al-Jaafari and its crimes. Otherwise it will suffer the same fate as that of the crusaders," said the tape.
"Any religious group that wants to be safe from the blows of the mujahidin must [disavow] the government of al-Jaafari and its crimes. Otherwise it will suffer the same fate as that of the crusaders"
Internet audio clip attributed to Abu Musab al-Zarqawi
At the same time, "any tribe ... whose allegiance to the crusaders and their agents is proven will be targeted by the mujahidin in the same way the crusaders are".
The term crusaders is usually applied to the US-led forces that ousted president Saddam Hussein in 2003 and that back the al-Jaafari government.
Al-Zarqawi, the one-legged fugitive with a $25-million price on his head, also urged Sunni Arabs to "wake up from your slumber ... the war to exterminate Sunnis will never end".
Iraq's most wanted man also challenged Iraqi leaders to leave the highly fortified "Green Zone" in Baghdad where the seat of government is located, to challenge his mujahidin or warriors.
Al-Zarqawi was reported injured in May and is said to have been treated in an Iraqi hospital.
He has never released a videotaped message. Only grainy identity shots, old images from Afghanistan and more recent photos of a portly, grizzled figure give any clue as to his appearance.