KHAZER CAMP, Iraq — U.S. planes and drones launched four airstrikes on Islamic State forces Saturday as they fired indiscriminately on Yazidi civilians taking shelter in the Sinjar mountains, U.S. Central Command said.

The strikes, which were spread out during the day, destroyed armored carriers and a truck, according to the Central Command statement. It was the third round of airstrikes against Islamic State forces by the U.S. military since they were authorized by President Obama on Thursday.

The military support also has been helping clear the way for aid flights to drop food and water to thousands of starving refugees in the Sinjar area.

But the help comes too late for many of the religious minorities targeted for elimination by the Islamic State group, which swept past U.S.-trained and equipped Iraqi government forces in recent weeks and now controls much of Iraq.

A delayed response by the Shiite-led government in Baghdad left Kurdish forces struggling to contain the Sunni extremists’ advances. With nowhere to go but uphill, Kurdish-speaking Yazidi refugees sought shelter in the mile-high Sinjar mountains, where their ancient religion holds that Noah’s ark came to rest.

U.S., Iraqi and British cargo planes dropped tons of food, water, tents and other equipment to the refugees Friday and Saturday. Iraq’s defense ministry released a video showing people in the Sinjar mountains rushing to collect food and water as the Iraqi government’s fleet of C130 cargo planes dropped 20 tons of aid at a time.

But at least 56 children have died of dehydration in the mountains, UNICEF’s spokesman in Iraq, Karim Elkorany, told The Associated Press on Saturday.

British officials estimated Saturday between 50,000 and 150,000 people could be trapped on the mountain.

And Juan Mohammed, a local government spokesman in the Syrian city of Qamishli, told The Associated Press that more than 20,000 starving Yazidis are fleeing across the border, braving gunfire through a tenuous “safe passage” that Kurdish peshmerga forces are trying to protect.