WASHINGTON — President Barack Obama vowed this morning that the United States would “work with the Libyan government to bring to justice” those who killed U.S. ambassador Chris Stevens and three other American personnel in an attack on the consulate in Benghazi.

“Make no mistake. Justice will be done,” he said in an appearance at the Rose Garden outside the White House.

Obama, who ordered an increased in security at U.S. facilities overseas, said he “condemns in the strongest possible terms the outrageous and shocking” attack.

He spoke after Republican presidential challenger Mitt Romney condemned the attack, and criticized the administration for its initial response to a separate incident on Tuesday, the breach of the U.S. embassy in Cairo.

“Make no mistake we will work with the Libyan government to bring to justice the killers who attacked our people,” he said, referring to the events in Libya.

He also said, “We reject all efforts to denigrate the religious beliefs of others, but there is absolutely no justification for this type of senseless violence, none.”

The incidents in both Arab countries were reportedly the work of protesters angry over a film that ridiculed Islam's Prophet Muhammad.