The U.S. State Department says a bomb blast that struck a U.S. Embassy vehicle in Lebanon's capital, Beirut, has killed four people.
Lebanese security officials put the death toll lower, at three.
Speaking in the Saudi capital, Riyadh, Secretary of State Condoleezza Rice expressed outrage at the blast and called it a terrorist attack. She said the U.S. will not be deterred in its efforts to help the Lebanese people and the democratic process in that country.
State Department spokesman Sean McCormack says no American diplomats were in the U.S. Embassy vehicle at the time of the blast, but that the Lebanese driver was slightly injured.
At least 16 people were wounded in the blast.
McCormack says an American was among those injured but was not in the U.S. embassy car.
There has been no claim of responsibility.
Television footage showed damaged cars on streets in a mainly Christian suburb of north Beirut (Qarantina), and smoke rising over the city.
A series of bombings in Lebanon in recent years mainly has targeted prominent anti-Syrian politicians. Syria has denied involvement in any of the attacks.
Last month, a car bombing killed Lebanese Brigadier General Francois al-Hajj on the outskirts of Beirut. He played a a key role in the army offensive against al-Qaida-inspired militants at a Palestinian refugee camp, Nahr al-Bared, last year.
Some information for this report was provided by AFP, AP and Reuters.