Prime Minister Yildirim said a group within Turkey's military had attempted to overthrow the government and security forces have been called in to "do what is necessary".
2203 - Turkish justice minister says members of a movement loyal to US -based cleric Fethullah Gulen in the army are behind the attempted coup.
A report from the U.S. Embassy in Ankara said military-appearing jets had been flying low over the city and Istanbul for about an hour.
The extraordinary session began with a minute of silence in honor of those who lost their lives during the coup, followed by the singing of the national anthem.
U.S. Secretary of State John Kerry attends a joint news conference with Russian Foreign Minister Sergei Lavrov following their meeting in Moscow, Russia, on Saturday.
On Saturday, activists - notably those linked to Hamas - called for demonstrations in solidarity with the Turkish government. Authorities also removed 2,745 judges from duty, according to Turkish broadcaster NTV. No reason has been given.
The Pentagon said there was no impact on operations against Islamic State from the US air base at Incirlik in Turkey.
He has been accused by Turkish President Recep Tayyip Erdogan of being behind Thursday's bloody coup attempt, although he himself has denied any role and condemned the military uprising "in the strongest terms".
In Istanbul, gunfire was heard and military vehicles blocked key bridges and access to the airport while fighter jets flew over the capital Ankara.
Even before the violent coup attempt, Obama had expressed concern over Erdogan's handling of the media and the rule of law. "I've never seen anything more powerful than the people", he said.
He said: "They will pay a heavy price for this".
"One of the key members of North Atlantic Treaty Organisation will now face a severe crisis in its military, and this will have severe repercussions on NATO's strength and fight against ISIS", Aykan Erdemir, a former member of Turkish parliament and current senior fellow at the Foundation for the Defence of Democracies, told Business Insider on Saturday. At least one bomb hit the parliament complex. MPs hid in shelters.
By Saturday morning, the mood had changed as pro-democracy activists in Egypt took to social media networks to post jubilant comments about the failure of the coup and publish photos of army officers and soldiers captured by civilians. When CNN Türk came back on air, anchorwoman Nevsin Mengu and general manager Erdogan Aktas described the mood of the young soldiers. CNN Turk later tweeted a photo of soldiers being arrested by police.
Explosions were reported at the Turkish parliament in Ankara and it was reported that 17 police officers had been killed in a helicopter attack on police special forces headquarters on the outskirts of the capital.
A Blackhawk military helicopter with seven Turkish military personnel and one civilian landed in the Greek city of Alexandroupolis, where the passengers requested asylum, according to Greece's defense ministry.
Turkish soldiers secure the area as supporters of Turkey's President Recep Tayyip Erdogan protest in Istanbul's Taksim square, early Saturday, July 16, 2016. Yildirim said that the situation is under the control of the official government.
Gulen sharply rejected any responsibility: "As someone who suffered under multiple military coups during the past five decades, it is especially insulting to be accused of having any link to such an attempt".
Although the chief of staff had been rescued, several military commanders were still being held hostage, he said. The militaries blocked the roads in Istanbul and Ankara with tanks, closed airports, bombed the parliament buildings, and stormed the intelligence headquarters and presidential palace.
Nato, of which Turkey is a member, called for "full respect" for Turkey's democratic institutions.
Newspapers have been taken over by the state, and journalists imprisoned for, among other things, endangering national security with scoops on Turkey's activities in the neighbouring civil war.