Ankara: The Turkish military has said that it had launched a coup, in what the prime minister termed an illegal act aimed at usurping the authorities.
Soldiers were seen on the streets in Istanbul and Ankara as jets flew low overhead, while ordinary citizens rushed for the safety of their homes after witnessing the coup attempt.
"The power in the country has been seized in its entirety," said a military statement quoted by Turkish media.
It said the move had been made "in order to ensure and restore constitutional order, democracy, human rights and freedoms and let the supremacy law in the country prevail, to restore order which was disrupted."
"All our international agreements and commitments retain their validity. We hope our good relations will continue with all countries in the world."
Television pictures showed tanks deployed outside Ataturk airport in Istanbul. Reports said that flights into the airport had been halted.
AFP correspondents said that Istanbul had been turned into a ghost town after the events, with people who had been outside for a Friday night rushing to the safety of their homes.
Turkish Prime Minister Binali Yildirim on Friday denounced what he said was an "illegal attempt" by elements in the military.
"We are working on the possibility of an attempt. We will not allow this attempt," he told NTV television by telephone, without expanding on the nature of the move but saying it was by a group in the Turkish military.
"Those who are in this illegal act will pay the highest price," he added, saying it would not be correct to describe the move as a "coup".
Turkey has a history of coups with governments ousted on three occasions in the last decades by full military coups.
However analysts had usually assumed that the ruling Justice and Development Party (AKP) of President Recep Tayyip Erdogan had good relations with the military.
There has been no comment from Erdogan so far.
But presidential sources said: "This is an attack against Turkish democracy. A group within the Armed Forces has made an attempt to overthrow the democratically elected government outside the chain of command.
"The statement made on behalf of the Armed Forces wasn't authorised by the military command. We urge the world to stand in solidarity with the Turkish people," the sources added.