Mr. Obama, Vice President Joe Biden and Secretary of State Hillary Clinton greeted the plane as it arrived at Andrews Air Force Base.
"Even as voices of suspicion and mistrust seek to divide countries and cultures from one another, the United States of America will never retreat from the world. We will never stop working for the dignity and freedom that every person deserves," the president said.
Across the Muslim world, protesters continue to rage for a fourth day against the United States and against the makers of the anti-Islam film that was produced in California. There are reports the U.S. embassies in Tunisia and Sudan have been breached.
Several thousand battled with Tunisian security forces outside the U.S. Embassy in Tunis. Protesters rained down stones on police firing volleys of tear gas and shooting into the air. Some protesters scaled the embassy wall and stood on top of it, planting an Islamist flag with the Muslim profession of faith, "There is no god but Allah and Muhammad is his prophet."
Police chased them off the wall and took the flag down. Two protesters were killed and 29 people were wounded, including police.
In Sudan, a prominent sheik on state radio urged protesters to march on the German Embassy to protest alleged anti-Muslim graffiti on mosques in Berlin and then to the U.S. Embassy to protest the film.
Soon after, several hundred Sudanese stormed into the German Embassy, setting part of an embassy building aflame along with trash bins and a parked car. Several thousand then moved on the American Embassy. They tried to storm the mission, clashing with Sudanese police, who opened fire on some who tried to scale the compound's wall. It was not clear whether any protesters made it into the embassy grounds.
Protests have also spread to other parts of the world, including Jerusalem, Afghanistan and Indonesia, where protesters chanted anti-American slogans and confronted authorities. More protests are expected. Many of the demonstrations broke out after Friday prayers.
Security forces in Yemen on Thursday shot live rounds in the air and fired tear gas at a crowd of around 2,000 protesters trying to march to the U.S. embassy in the capital city of Sanaa.
Four people have been arrested in connection with the attack in Libya that killed four Americans: U.S. Ambassador Chris Stevens; Sean Smith, an Air Force veteran who worked as an information management specialist for the State Department; 41-year-old Tyrone Woods of Imperial Beach, who was working as security for the ambassador and the U.S. delegation; and 42-year-old Glenn Doherty from Encinitas.
"Glen was an amazing human being, and we're devastated. He was a great friend and brother and really good at his job. It's a huge loss for everyone," said Katie Quigley, Doherty's sister.
Family members said both of the California men are former Navy SEALs, and they loved what they were doing.
"This is what he loved to do. He was helping keep people safe. To me, he really needs to be honored for putting himself out there like that to serve our country," said Patricia Ann So, Woods' former wife.
Investigators said the attack on the Libyan consulate started as a protest against the YouTube trailer of the anti-Islam film, "Innocence of Muslims." They now suspect organized terror cells in Libya then took advantage of the protest to attack the consulate.
Law enforcement officials in the U.S. are concerned extremists may try and capitalize on the unrest. They are warning Americans to be vigilant and report any suspicious activities.
