Tensions between Turkey and the US have escalated following the attempted coup against the Erdogan administration, with the country's leader demanding the extradition of a US-based cleric accused of orchestrating the violence. Another senior official has directly blamed the United States.

The Obama administration has strongly denied any involvement or responsibility in recent events in the country. In a phone call to his counterpart in Turkey, US Secretary of State John Kerry said: “Public insinuations or claims about any role by the United States in the failed coup attempt are utterly false and harmful to our bilateral relations."

The warning came after Turkey closed its airspace, thereby effectively grounding US warplanes which have been targeting Isis forces in neighbouring Syria and Iraq.

Earlier today, Turkey's justice minister Bekir Bozdag announced that some 6,000 people have now been detained in a government crackdown on suspected opponenents and dissenters following the coup.

In a television interview Minister Bozdag said: "The cleansing [operation] is still continuing. Some 6,000 detentions have taken place. The number could surpass 6,000."

Turkey failed coup: People stand up to military

At the centre of the controversy stands Fethullah Gulen, who lives in exile in Pennsylvania and promotes a philosophy that blends a mystical form of Islam with staunch advocacy of democracy, education, science and interfaith dialogue.

In a televised speech on Saturday, President Erdogan said Turkey had never rejected a US extradition request for “terrorists.” Addressing Washington, he requested the handover of Gulen and said, “If we are strategic partners, then you should bring about our request.”

Addressing Barack Obama on Saturday, the Turkish Prime Minister Binali Yildirim said: “Any country that stands behind him is no friend of Turkey, is engaged in a serious war with Turkey. Today, after this coup attempt, I’m once again calling on you, I’m saying: Extradite this man in Pennsylvania to Turkey now."

Suleyman Soylu, Turkey's labor minister, went further than Erdogan, suggesting the U.S. was behind the coup. "The US is behind the coup attempt. A few journals that are published there [in the US] have been conducting activities for several months. For many months we have sent requests to the US concerning Fethullah Gulen. The US must extradite him," he said.

Gulen has condemned Friday night's coup attempt by military officers that resulted in a night of explosions, air battles and gunfire that left dozens dead. Erdogan's government said Gulen directed the coup all the same.

Although he didn't outline any threat, Erdogan's emphasis on US-Turkish counterterrorism cooperation raised the prospect of a prolonged closure of the Incirlik air base in southern Turkey if he didn't get his way. The Pentagon said it was trying to get permission to resume air operations from the base, while adjusting mission operations in the meantime.

In their second call in as many days, Turkish Foreign Minister Mevlut Cavosoglu told Kerry the government was in control of state institutions.

Kerry reiterated U.S. support for Turkey's democratically elected government, according to the State Department readout, and urged authorities to respect the rule of law and safeguard civilian life as they respond to the coup attempt. Kerry also said Turkey needed to respect due process as it investigates those it believes were involved in the plot.

Earlier, on a visit to Luxembourg, Kerry told reporters the U.S. would entertain an extradition request for Gulen if the Turks provided evidence of wrongdoing. Erdogan has long accused Gulen, a former ally, of trying to overthrow the government, but Washington has never found the claims compelling.

“We fully anticipate that there will be questions raised about Mr. Gulen,” Kerry told reporters. “And obviously we would invite the government of Turkey, as we always do, to present us with any legitimate evidence that withstands scrutiny. And the United States will accept that and look at it and make judgments about it appropriately.”

Gulen is understood to maintain significant support among some members of the military and mid-level bureaucrats. His movement called Hizmet includes think tanks, schools and various media enterprises. Gulen and Erdogan only became estranged in recent years.

A Turkish official, speaking on condition of anonymity in line with government regulations, said Turkey was preparing a formal extradition request with detailed information about Gulen's involvement in illegal activities. He said the coup attempt was seen as “one more thing to add to an already extensive list.”

In a statement, Gulen said he condemned, “in the strongest terms, the attempted military coup in Turkey” and sharply rejected any responsibility or knowledge of who might be involved.

At a news briefing Saturday in Saylorsburg, Pennsylvania, the cleric noted that he has been away from Turkey for more than 15 years and would not have returned if the coup had succeeded. He cited greater freedoms in the United States as a reason.

“In brief, I don't even know who my followers are,” the frail-looking cleric said through an interpreter. “You can think about many motivations of people who staged this coup.”

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

The coup failed after appearing not to have been backed by the most senior ranks of the military. Turkey's main opposition parties, too, condemned the attempted overthrow of the government. Prime Minister Benali Yildirim said 161 people were killed and 1,440 wounded in the overnight violence. He said 2,839 plotters were detained.

Kerry said the U.S. had no indication beforehand of the coup attempt, which began as he and Russia's foreign minister were in a Russian government villa in Moscow, locked in negotiations over Syria.