CNN reports that the strikes involved fighters, bombers and Tomahawk missiles; they hit the city of Raqqa, where ISIS has set up a stronghold. The New York Times reports that they also employed Predator and Reaper drones, and that targets included "weapons supplies, depots, barracks and buildings the militants use for command and control."
Rear Admiral John Kirby, the Pentagon Press Secretary, released a statement confirming the strikes. He said the decision to authorize the strikes was made today and approved by President Obama, but declined to provide much else in the way of detail, "given that these operations are ongoing."
— Zeke Miller (@ZekeJMiller) September 23, 2014
After French and American war planes hit ISIS targets in Iraq last week, the group has been encouraging its supporters to attack citizens of the United States, France and other countries that have joined the military coalition against them. The Arab nations in the coalition have not yet been publicly identified.
Update, 10:41: It looks like the first person to report the bombings wasn't with any news agency. He was a civilian in Raqqa named Abdulkader Hariri, who tweeted this as the strikes began:
Breaking: Huge explosions shook the city in what might be the beginning of US airstrikes on ISIS HQs in Raqqa
— Abdulkader Hariri (@3bdUlkaed6r) September 23, 2014
Hariri continued to live-tweet the bombing of his city for about an hour before falling silent.
[Image of Pentagon Press Secretary John Kirby via Wikimedia Commons]