An army group in Turkey says it has taken over the country, with soldiers at strategic points in Istanbul and jets flying low in the capital, Ankara.
A statement read on TV said a "peace council" now ran the country and there was a curfew and martial law.
It is unclear who the group is or its level of support. Some top army officials are said to be detained.
President Recep Tayyip Erdogan said he would overcome what he called an uprising by a minority.
In Washington, US President Barack Obama urged all parties in Turkey to support the "democratically elected government".