Turkish President Tayyip Erdogan urged people to take to the streets to protest against what he described as a coup attempt by a minority faction within the military, vowing that it would meet with a "necessary response".
He told a CNN Turk reporter via cellphone that Turkish people must gather in public squares to show their response to the attempted military takeover, in comments broadcast live on television.
Erdogan said he believed the attempted coup would be over within a "short time" and said those responsible would pay a heavy price in the courts.
He said the act was encourage by the "parallel structure" - his shorthand for followers of Fethullah Gulen, a U.S.-based Muslim cleric who he has repeatedly accused of attempting to foment an uprising among his followers in the judiciary and the military.
The Turkish military on Friday 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."