Annan, speaking at a press conference with Iraqi Prime Minister Ibrahim Ja'fari, emphasized the importance of "reconciliation" in Iraq.
The unannounced visit to Iraq is Annan's first since U.S.-led invasion forces ousted former leader Saddam Hussein in April 2003.
As Annan's arrival was announced, a car bomb exploded in a market in east Baghdad. Police said at least four people were killed and more than 20 others injured in the incident.
(Reuters/AFP/AP)