The U.S. military and Arab allies attacked Sunni militants in the Islamic State in Syria early Tuesday. They launched airstrikes, and the NY Times reported, “a torrent of cruise missiles and precision-guided bombs from the air and sea on the militants’ de facto capital of Raqqa, the northeastern Syrian city, and along the porous Iraq border.”

The Washington Post reported that residents of Raqqa reported large explosions on Twitter and said repeated passes from military aircraft were clearly audible.

Among the weapons used by American and Arab forces were Tomahawk cruise missiles, American and Arab jet fighters, armed Predator and Reaper drones. According to Rear Admiral John Kirby, the spokesman for the Pentagon, the targets included weapons supplies, depots, barracks and buildings the militants use for command and control. Tomahawk cruise missiles were fired from United States Navy ships in the region.

He said the operations were ongoing and that more details would not be released until after the strikes were finished and that “partner nation forces” were also involved in the attacks but did not identify which other countries participated. The attacks were the largest attacks on any given day since attacks began against the jihadist group in Iraq on Aug. 8.

The Post said military officials, who spoke off the record, said the targets included buildings occupied by Islamic State leaders and the group’s training sites and arsenals. The CIA believes ISIS has up to 31,000 fighters at its disposal and uses Syria as a springboard to attack Iraq. It also threatens Jordan and other bordering countries.

The Post said it was unclear how Assad’s armed forces would respond to unauthorized intrusions into Syrian airspace by U.S. warplanes. The Syrian government has some of the most formidable air defenses in the Middle East. Obama had publicly warned Syria in advance not to interfere with any U.S. operations against the Islamic State, saying the Pentagon would respond forcefully. In the end, U.S. military planners said they expected Assad would stand down and allow them to attack Islamic State targets freely.

Admiral Kirby said, “The decision to conduct these strikes was made earlier today by the U.S. Central Command commander under authorization granted him by the commander in chief. We will provide more details later as operationally appropriate.”