The U.S. ambassador to Libya and three American staffers were killed in an attack Tuesday on the U.S. consulate in the Libyan city of Bengahzi.

Fox News reports the White House has confirmed the deaths of the four Americans. President Obama issued a written statement this morning in which he called the attack "outrageous" and "senseless."

Fox News says Ambassador J. Christopher Stevens was killed when he and a group of embassy employees went to the consulate and tried to evacuate staff. The group encountered protestors, angry over a film that ridiculed Islam's Prophet Muhammad, who were firing gunshots and rocket-propelled grenades.

Stevens was appointed as ambassador to Libya in May 2012.

President Obama said he's directed the administration to provide "all necessary resources" to support security for U.S. personnel in Libya and to increase security at diplomatic offices around the world. U.S. officials remain on alert for violence at other diplomatic posts.