The swift rounding up of judges and others accused of taking part in a failed coup in Turkey indicates the government had prepared a list beforehand, the EU commissioner dealing with Turkey's membership bid has said.

Following a failed coup attempt on Saturday, Turkish authorities on Sunday rounded up nearly 3,000 suspected military plotters, ranging from top commanders to foot soldiers, and the same number of judges and prosecutors.

"It looks at least as if something has been prepared," Johannes Hahn said. "The lists are available, which indicates it was prepared and to be used at a certain stage.

"I'm very concerned. It is exactly what we feared."

In pictures: Turkey coup attempt Show all 17 1 /17 In pictures: Turkey coup attempt In pictures: Turkey coup attempt Turkish President Erdogan attends the funeral service for victims of the thwarted coup in Istanbul at Fatih mosque on July 17, 2016 in Istanbul, Turkey Burak Kara/Getty Images In pictures: Turkey coup attempt Soldiers involved in the coup attempt surrender on Bosphorus bridge with their hands raised in Istanbul on 16 July, 2016 Gokhan Tan/Getty In pictures: Turkey coup attempt A civilian beats a soldier after troops involved in the coup surrendered on the Bosphorus Bridge in Istanbul, Turkey, 16 July, 2016 REUTERS/Murad Sezer In pictures: Turkey coup attempt Surrendered Turkish soldiers who were involved in the coup are beaten by a civilian Reuters In pictures: Turkey coup attempt Soliders involved in the coup attempt surrender on Bosphorus bridge Getty In pictures: Turkey coup attempt Supporters of Turkish President Recep Tayyip Erdogan wave flags as they capture a Turkish Army vehicle Getty In pictures: Turkey coup attempt People pose near a tank after troops involved in the coup surrendered on the Bosphorus Bridge in Istanbul, Turkey, 16 July, 2016 Reuters In pictures: Turkey coup attempt Turkish soldiers block Istanbul's Bosphorus Brigde Getty In pictures: Turkey coup attempt A Turkish military stands guard near the Taksim Square in Istanbul Reuters In pictures: Turkey coup attempt Pierre Crom/Twitter In pictures: Turkey coup attempt Turkish soldiers secure the area as supporters of Recep Tayyip Erdogan protest in Istanbul's Taksim square AP In pictures: Turkey coup attempt People demonstrate in front of the Republic Monument at the Taksim Square in Istanbul Murad Sezer/Reuters In pictures: Turkey coup attempt Turkish soldiers detain police officers during a security shutdown of the Bosphorus Bridge Reuters In pictures: Turkey coup attempt Turkish Army armoured personnel carriers in the main streets of Istanbul Getty In pictures: Turkey coup attempt Chaos reigned in Istanbul as tanks drove through the streets EPA/TOLGA BOZOGLU In pictures: Turkey coup attempt Turkish President Tayyip Erdogan speaks to media in the resort town of Marmaris Reuters In pictures: Turkey coup attempt Supporters of President Erdogan celebrate in Ankara following the suppression of the attempted coup Reuters

It appears, Mr Hahn added, as if Turkey had "prepared" arrest lists of political opponents and was waiting for the right time to act.

Observers said the scale of the crackdown, especially against the judiciary, indicated the government was taking the opportunity to further consolidate Mr Erdogan's power.

Conspiracy theorists are saying the attempted military coup was faked, comparing it to the Reichstag fire - the 1933 arson attack on the German parliament building used by Hitler as an excuse to suspend civil liberties and order mass arrests of his opponents.

Some of the soldiers detained following the coup reportedly told interrogators they were not aware they were part of a coup attempt and had been told by commanders they were taking part in military manoeuvres.

Turkey rounds up thousands after failed coup

Reports have emerged that rebel jets had President Erdogan's plane in their sights during the coup but did not fire.

"Why they didn't fire is a mystery," a former military officer told Reuters.

The European Union and the United States expressed alarm at Turkey's response to the coup, telling the NATO member and EU aspirant it must uphold democracy and human rights as it pursues the military officers and anyone else involved in the plot.

"This is no excuse to take the country away from fundamental rights and the rule of law, and we will be extremely vigilant on that," EU foreign policy chief Federica Mogherini said at a joint news conference with US Secretary of State John Kerry.

The top American diplomat said Turkey must "uphold the highest standards for the country's democratic institutions and the rule of law."

While he recognised the need to apprehend the coup plotters, Mr Kerry said: "We caution against a reach that goes beyond that."