Security is being beefed up at the U.S. embassy in the capital of Iraq and some staff members are being temporarily moved to other parts of Iraq and to Jordan.
A State Department spokeswoman says in a statement that a "substantial majority" of U.S. embassy staff will remain even as parts of the country experience instability and violence.
She says the Baghdad embassy will continue to engage daily with Iraqis.
U.S. travelers in the country were encouraged to exercise caution and limit travel to certain parts of Iraq.
An al-Qaida splinter group surprised Western intelligence organizations last week and took control of major Iraqi cities.