A magnitude 7.8 earthquake struck Turkey early Monday and was followed by a powerful aftershock that was felt across the region in Syria and Lebanon.

The earthquake hit at 4:17 a.m. near the city of Nurdagi, according to the United States Geological Survey. It had a depth of about 10 miles. An aftershock measured 6.7.

In an assessment, the agency said that significant casualties were likely and there may be hundreds of fatalities.

This is a developing story.