By Humeyra Pamuk and Nick Tattersall

ISTANBUL (Reuters) – Turkey will announce emergency measures on Wednesday to try to shore up stability and prevent damage to the economy as it purges thousands of members of the security forces, judiciary, civil service and academia after an abortive coup.

Around 50,000 soldiers, police, judges, civil servants and teachers have been suspended or detained since the military coup attempt, raising tensions across the country of 80 million which borders Syria’s chaos and is a Western ally against Islamic State.

Academics were banned from traveling abroad on Wednesday in what a Turkish official said was a temporary measure to prevent the risk of alleged coup plotters in universities from fleeing. State TRT television said 95 academics had been removed from their posts at Istanbul University alone.

“Universities have always been crucial for military juntas in Turkey and certain individuals are believed to be in contact with cells within the military,” the official said.

President Tayyip Erdogan blames the network of U.S.-based cleric Fethullah Gulen for Friday night’s attempted coup, in which more than 230 people were killed as soldiers commandeered fighters jets, military helicopters and tanks to try to overthrow the government.

Erdogan has vowed to clean the “virus” responsible for the plot from all state institutions. The depth and scale of the purges have raised concern among Western allies that Erdogan is trying to suppress all dissent, and that opponents unconnected with the plot will be caught in the net.

He will chair meetings in his palace on Wednesday of the cabinet and the National Security Council, after which a series of emergency measures are expected to be announced.

In a sign of how shaken Turkey’s leadership has been by the coup attempt, with dozens of generals arrested as well as Erdogan’s aide de camp, government ministers and top officials have not been briefed in advance of the meetings.

“The cabinet meeting is classified at the highest level for national security reasons. The palace will give ministers a dossier just beforehand,” one senior official told Reuters.

“Ministers do not yet know what is going to be discussed.”

Around a third of Turkey’s roughly 360 serving generals have been detained since the coup bid, a second senior official said, with 99 charged pending trial and 14 more being held.

The threat of prolonged instability in a NATO member country, which had not seen a violent military coup for more than three decades, has shaken investors’ confidence.

The lira hit a 10-month low in early trade on Wednesday, touching 3.063 to the dollar. The Istanbul stock index is down 8 percent so far this week, its worst three-day performance since 2013. The cost of insuring Turkish debt against default rose to its highest in nearly a month, according to data from Markit.

Deputy Prime Minister Mehmet Simsek told Reuters a priority in the measures to be discussed on Wednesday would be preventing damage to the economy. He also said on Twitter they would be “market-friendly” and would prioritize structural reform.

MILITARY CHIEF REFUSED TO BACK COUP BID

Around 1,400 people were wounded as soldiers commandeered tanks, attack helicopters and warplanes, strafing parliament and the intelligence headquarters and trying to seize the main airport and bridges in Istanbul.

At the height of the abortive coup, the rebel pilots of two F-16 fighter jets had Erdogan’s plane in their sights as he returned to Istanbul from a holiday on the coast. Erdogan said he was almost killed or captured by the mutineers.

In testimony published by the Hurriyet newspaper and corroborated by a Turkish official, an infantry lieutenant-colonel said the coup plotters had tried to persuade military chief Hulusi Akar, who was being held hostage, to join the effort to overthrow Erdogan but that he had refused.

“When he refused, they couldn’t convince the senior commanders either. Akar’s refusal to be a part of this paved the way for the failure of the coup attempt,” the written transcript published by the newspaper said.

Erdogan, Prime Minister Binali Yildirim, ministers, senior commanders and generals had been due to be taken one by one during the night of the coup bid, the testimony said.

Turkey’s Western allies have expressed solidarity with the government over the coup attempt but have also voiced increasing alarm at the scale and swiftness of the response, urging it to adhere to democratic values.

On Tuesday, authorities shut down media outlets deemed to be supportive of Gulen and said 15,000 people had been suspended from the education ministry along with 100 intelligence officials. A further 492 people were removed from duty at the Religious Affairs Directorate, 257 at the prime minister’s office and 300 at the energy ministry.

Those moves come after the detention of more than 6,000 members of the armed forces, from foot soldiers to commanders, and the suspension of close to 3,000 judges and prosecutors. About 8,000 police officers, including in the capital Ankara and the biggest city Istanbul, have also been removed.

U.N. High Commissioner for Human Rights, Zeid Ra’ad Al Hussein, voiced “serious alarm” on Tuesday at the mass suspension of judges and prosecutors and urged Turkey to allow independent monitors to visit those who have been detained.

The foreign ministry has said criticism of the government’s response amounts to backing the coup.

TENSIONS WITH U.S.

Erdogan’s spokesman said on Tuesday the government was preparing a formal request to the United States for the extradition of Gulen. U.S. President Barack Obama discussed the status of Gulen in a telephone call with Erdogan on Tuesday, the White House said, urging Ankara to show restraint as it pursues those responsible for the coup attempt.

Seventy-five-year-old Gulen, who lives in self-imposed exile in Pennsylvania but has a network of supporters within Turkey, has condemned the abortive coup and denied any role in it.

A former ally-turned critic of Erdogan, he suggested the president staged it as an excuse for a crackdown after a steady accumulation of control during 14 years in power.

Prime Minister Yildirim accused Washington, which has said it will consider Gulen’s extradition only if clear evidence is provided, of double standards in its fight against terrorism.

Yildirim said the justice ministry had sent a dossier to U.S. authorities on Gulen, whose religious movement blends conservative Islamic values with a pro-Western outlook and who has a network of supporters within Turkey.

White House spokesman Josh Earnest confirmed Ankara had filed materials in electronic form with the U.S. government, which officials were reviewing. Any extradition request from Turkey, once submitted, would be evaluated under the terms of a treaty between the two countries, he added.

Such a request would face legal and political hurdles in the United States. Even if approved by a judge, it would still have to go to Secretary of State John Kerry, who can consider non-legal factors, such as humanitarian arguments.

“I urge the U.S. government to reject any effort to abuse the extradition process to carry out political vendettas,” Gulen said on Tuesday in a statement issued by the Alliance for Shared Values, a group associated with the cleric.

(Additional reporting by Orhan Coskun, Humeyra Pamuk, Can Sezer and David Dolan; Writing by Nick Tattersall and Philippa Fletcher; Editing by David Stamp)