ISTANBUL — The Turkish government said Saturday it had suppressed a coup by a military faction and arrested thousands of soldiers after a chaotic night that saw armed attacks on the national parliament and an apparent assassination attempt against President Recip Tayyip Erdogan.

The coup attempt stunned this nation of nearly 80 million, a key U.S. NATO ally, and raised new questions about its long-term stability as well as its future role in the fight against Islamic State extremists and its response to the civil war in neighboring Syria.

The big unanswered question Saturday was the motive of the coup, which the government immediately blamed on Erdogan’s former ally, Fethullah Gülen, a Muslim cleric now living in exile in the U.S. Erdogan had been planning a major military purge next month, directed against any Gulenist supporters who hadn’t already been removed from the military ranks, and it’s possible that fear of losing their jobs united the officers behind the coup.

The purge would have added still more to Erdogan’s control over of Turkish political life. Already in control over much of the news media, he is now attempting to extend his grasp over the judiciary and is pressing hard for a change in the constitution that will give him far greater executive powers.

The government said 161 people were killed in the coup attempt, and 1,440 wounded. In addition, 104 soldiers identified as coup backers were killed in the fighting. It said 2,839 member of the military had been arrested. Erdgogan made it clear they will be treated as traitors and terrorists.

One group of eight military personnel fled by helicopter to Greece, and Foreign Minister Mevlut Cavusoglu said he had formally requested their extradition.

If the coup plotters had expected a popular upswell of support, they were fatally mistaken. The masses of people who took to the streets did so to back Erdogan. Even the opposition parties made it clear they were against what would have been the fifth military overthrow of a civilian government, whether by force or menacing memorandum, since 1960.

“Friday night was a stain in the history of Turkish democracy,” Prime Minister Binali Yildirim said Saturday morning.

As he congratulated Turkish citizens for resisting the coup attempt, he noted that the military chain of command did not support the rebels. Indeed, the coup organizers detained chief of staff Gen. Hulusi Akar in his headquarters until a commando team reportedly rescued him in the middle of the night.

Erdogan and Yildirim both blamed the coup on officers sympathetic to a movement headed by former Turkish cleric Fethullah Gülen, who now lives in U.S. exile in the foothills of Pennsylvania’s Poconos mountains.

“It was an action taken by the Gulenist group within the armed forces,” Yildirim said as he demanded that the United States extradite Gülen to face charges here. Erdogan, not mentioning his name, nonetheless called on him to return to Turkey to face trial: “The betrayal you have done to this nation is enough,” he said.

But Gülen issued a statement condemning the military attempt to take over the government.

The coup attempt began at about 7:30 p.m. Friday night local time, when the dissident military faction sent tanks to close Istanbul’s two bridges over the Bosporus strait linking Europe with Asia.

Declaring that it was in complete charge of the country, the faction announced a national curfew, seized the General Staff headquarters, took over state television and sent tanks to surround the Turkish parliament. Later the faction carried out bombing raids against the parliament as well as other key security installations.

Erdogan, who was vacationing on the Aegean coast, appealed to his followers to take to the streets in protest and said he was flying to Ankara. Instead he landed early Saturday in Istanbul’s Ataturk airport, where he said the coup plotters had bombed the resort hotel in Marmaris hours after he had departed.

Erdogan could not have flown safely to Ankara, because rebel warplanes and helicopters dominated the skies. The government responded by closing the airspace over the capital and ordering its own warplanes to shoot down what it called “hijacked” government aircraft. As government supporters took to the streets to demonstrate against the coup, fighting between dissidents and loyal troops was reported through the night.

As of Saturday midday, some 150 military coup supporters were still holding out at a major base in Ankara, the government said.

Istanbul was relatively quiet, and there was no sign that anyone was observing the nationwide curfew called by the coup leaders, but starting at about 3:30 a.m., warplanes, apparently piloted by dissidents, criss-crossed the skies repeatedly at low altitudes, causing repeated sonic booms. It may have been one of the last gasps of the rebellion.

The U.S. embassy urged American citizens to stay indoors and not to attempt to reach the main airports in Istanbul and Ankara. The embassy said in a special security message that it had reports of sporadic gunfire at Istanbul’s main Ataturk airport and said it had ordered government employees not to attempt to travel to or from the facility.

U.S. airlines were ordered to halt all flights to or from Istanbul or Ankara airports and all direct flights to and from the U.S. were cancelled.