The Pentagon says the U.S. and partner nations have begun airstrikes in Syria against Islamic State militants, using a mix of fighter jets, bombers and Tomahawk missiles fired from ships in the region.

Pentagon Press Secretary Rear Adm. John Kirby says that because the military operation is ongoing, no details can be provided yet. He says the decision to strike was made early Monday by the military.

The strikes are part of the expanded military campaign that President Barack Obama's authorized nearly two weeks ago in order to disrupt and destroy the Islamic State militants, who have slaughtered thousands of people, beheaded Westerners, including two American journalists, and captured a large swath of territory stretching from within Syria to land across northern and Western Iraq.