The videotape posting on the As-Sahab Media Web site is a departure from al-Qaida's usual policy of not advocating violence between the major divisions of Islam, CNN said.
The tape appeared on the site late Friday.
Sunnis controlled Iraq, despite the Shiite majority, under the Saddam Hussein regime until the U.S.-led invasion in 2003. The new Iraqi government is dominated by Shiites, with some Sunni and Kurd participation.
On the videotape, bin Laden calls Iraqi Shiites "rejectionist," "traitors" and "agents of the Americans," CNN said.
Bin Laden also names Abu Hamza al-Muhajer the new leader of al-Qaida in Iraq.
Another videotape purportedly of bin Laden surfaced Wednesday, and mourns the death of Jordanian Abu Musab al-Zarqawi, who headed the deadly al-Qaida in Iraq until he was killed by a U.S. airstrike.
A car bomb exploded in a predominantly Shiite market in Baghdad Saturday, killing more than 60.