Turkey's president has urged citizens to take to the streets in a show of support for the government after the military said it seized full control of the country.
Recep Tayyip Erdogan, speaking to CNN-Turk through FaceTime, called the actions by the military "an attempt at an uprising by a minority within our armed forces".
The president's office refused to disclose Erdogan's whereabouts, saying he was at a secure location.
Erdogan said "I don't believe this coup attempt will be successful.
"There is absolutely no chain of command here. Right now the chain of command has been put on hold."
Loud explosions were heard in Turkey's capital Ankara and CNN-Turk reported an explosion at the state-run television building.
Turkey's state-run news agency said military helicopters had also attacked the headquarters of TURKSAT satellite station on the outskirts of Ankara and the Ankara police headquarters.
Dozen of tanks were seen moving towards a palace that is now used by the prime minister and deputy prime ministers.
A civilian car tried to stop one of the tanks, but it rammed through the vehicle as those in the car escaped.
The White House said President Barack Obama had been briefed on developments in the key Nato ally.
The National Security Council said Obama had been apprised the "unfolding situation" in Turkey and would continue to get regular updates.
US secretary of state John Kerry says he hoped for stability and continuity in Turkey following the reports.
Mr Kerry, in Moscow for talks with Russian officials on Syria, said he did not have details of the situation rapidly unfolding on the ground in Turkey and said it would be "inappropriate" to comment on developments.
But he expressed hope that the key ally and strategically important member of the coalition fighting the Islamic State would remain at peace.