The Turkish president has said a "clear crime of treason" has been committed by coup plotters and he will approve a decision to reinstate the death penalty if passed by parliament.

Authorities have fired nearly 9000 military officers, bureaucrats, police and others, while detaining thousands more alleged to have been involved in Friday night's attempted coup, which left more than 260 people dead.

Turkey abolished capital punishment in 2004 as the country sought to become a member of the European Union. After the failed coup attempt on Friday, there were calls to reinstate the death penalty.

Turkish President Recep Tayyip Erdogan, whose government survived the failed military coup, said he would ratify it if parliament approves.


"There is a clear crime of treason and your request (death penalty) cannot be rejected by our government. Parliament needs to discuss it and if the leaders agree and discuss it then I as president will approve any decision to come out of the parliament," he told CNN International on Monday evening.

"Why should I keep them and feed them in prisons, for years to come? That's what the people say.

"They want a swift end to it, because people lost relatives, neighbours, children... they're suffering so the people are very sensitive and we have to act very sensibly and sensitively."

Turkey has also seen a spate of bombings in recent months blamed on the Islamic State group and Kurdish rebels.

The EU has called on Turkish authorities to exercise restraint, saying the reinstatement of the death penalty would threaten its membership bid.

Amnesty International warned on Monday that human rights were in "grave danger."

Amnesty's director for Europe and Central Asia John Dalhuisen said the sheer number of arrests and suspensions since Friday were "alarming".

"Cracking down on dissent and threatening to bring back the death penalty are not justice," he said.

Thousands of people have been dismissed or detained in the judiciary, interior ministry, military and police following Friday's failed coup.

The large scale of the crackdown has also alarmed Turkey's key allies, the United States and the European Union.

Amnesty said it was investigating reports that detainees in Ankara and Istanbul had been subjected to a series of abuses, including ill-treatment in custody and being denied access to lawyers.

Meanwhile, Human Rights Watch Europe and Central Asia Director Hugh Williamson noted: "The speed and scale of the arrests, including of top judges, suggests a purge rather than a process based on any evidence. Turkey's citizens who took to the streets to defend democracy deserve a response that upholds the rule of law."