(CNN) -- Al-Jazeera broadcast Monday an audio message purportedly from al Qaeda leader Osama bin Laden calling on al Qaeda and other groups in Iraq to unify their forces and speak with one voice, that of the Islamic nation.
Osama bin Laden in an undated photograph.
The Arabic-language broadcaster said the tape was titled "Letter to the People of Iraq."
The message includes no dated references, making it impossible to determine when it was taped based on its contents. In the message, bin Laden calls on his followers to be loyal to the Islamic nation, not to individual leaders, groups, tribes or countries.
The tape marks the first time bin Laden speaks directly to the militants.
"Beware of your enemies, especially those who infiltrate your ranks," he said in Arabic.
"I advise myself and the Islamic nation not to follow individuals and countries," he said. "Everything should be seen in the light of Islam."
Addressing the mujahedeen in Iraq as "my brothers," he said, "You have done well to perform your duty, but some of you have been late to another duty, which is to unify your ranks and make them into one line." Watch description of tape purportedly from bin Laden »
Though CNN is not able to confirm that the voice belongs to bin Laden, the Arabic-language broadcaster has aired other tapes of his and the voice sounded like bin Laden's, said CNN Arabic Affairs senior editor Octavia Nasr.
Last month, an audio message from bin Laden called on Muslims to "carry out jihad" against Pakistan's president, Gen. Pervez Musharraf.
Last month's 23-minute audio message -- titled "Come to Jihad: A Speech to the People of Pakistan" -- was recorded over a montage of old video, and began with bin Laden reciting prayers and citations from the Quran in Arabic. The audio then faded, and a narrator translated bin Laden's message into Pashto. The tape was subtitled in English, and an Arabic transcript was released.
Terrorism analyst Laura Mansfield told CNN that while the September 20 message was directed at the Pakistani people, "the simultaneous release of transcripts in English, Pashto and Arabic indicate the terror group is looking at a wider audience, including the English-speaking world." E-mail to a friend
All About Osama bin Laden
The leader of al-Qaeda, Osama bin Laden, has released a new audiotape which was broadcast through ''Al Jazeera''. The tape is entitled ''Letter to the people of Iraq.''

On the tape, he reportedly calls for unity among insurgents in Iraq, but also says that insurgents have been "lax" in their duties. In the tape, bin Laden's main focus is on Iraq.

"Some of you have been lax in one duty, which is to unite your ranks. Beware of division ... The Muslim world is waiting for you to gather under one banner. The interest of the Islamic nation surpasses that of a group. The strength of faith is in the strength of the bond between Muslims and not that of a tribe or nationalism. Beware of your enemies, especially those who infiltrate your ranks. I advise myself and the Islamic nation not to follow individuals and countries. Everything should be seen in the light of Islam," said bin Laden on the tape.

The voice on the tape has yet to be confirmed to be that of bin Laden's and it is not known how the network received the tape.