The U.S. Geological Survey reported a magnitude of 7.3, though Turkey's National Earthquake Monitoring Center reported a magnitude of 6.6.
The USGS reported a depth of 4.5 miles, or 7.2 km; the center in Turkey said the quake was about 3 miles, or 5 kilometers, deep.
The quake took place 12 miles from Van, at 1:41 p.m. local time, the USGS said.
Video from CNN Turk showed the inside of shaking buildings, and people gathering outside on the streets.
The area is "no stranger to having these seismic events," but Sunday's quake is considered major, CNN Meteorologist Reynolds Wolf reported.
One concern is displacement of water along Lake Van, which could send water gushing into nearby areas, particularly along the west side, Wolf reported.