A Turkish prosecutor filed an indictment against Islamic cleric Fethullah Gulen on Thursday alleging that the CIA and the Federal Bureau of Investigation (FBI) in the US helped train members of his movement to plot this month's failed coup attempt.
Within days of the failed putsch in Turkey on July 15, rumours circulated that Washington, Ankara's key NATO ally, somehow had a hand in its planning.
The claims, made in media reports and even by Turkey's labour minister, were not backed up by hard evidence but have nevertheless gained traction in Turkey.
Thursday's indictment, filed in the north-western city Edirne and reported by the state-run Anadolu news agency, claims that the CIA and the FBI provided training at "cultural centres" to followers of Islamic preacher Fethullah Gulen.
Turkish President Recep Tayyip Erdogan and several Turkish opposition groups blame the coup on Turkish-born Gulen, who lives in the US state of Pennsylvania in self-imposed exile. They claim he ran a secret "parallel state" in Turkey, preparing for the coup.
Gulen's movement has a large network of educational institutions around the world, including a profitable network of charter schools in the US.
Washington has repeatedly rejected accusations that it had a hand in the bloody events that left more than 260 people dead and led to wide-ranging purges of tens of thousands of civil servants for their alleged connection to Gulen.
US ambassador John Bass even went on Turkish television last week to categorically reject the claims, saying: "The United States government did not direct, support or know about the coup."
Turkey is demanding that the US extradite Gulen. The US is demanding solid proof before deporting him. Allegations that Turkey tortured many alleged coup plotters in jail adds a hurdle.
The chairman of the US Joint Chief of Staff directly rejected the "absurd" claim that General John Campbell - the former US-led coalition commander in Afghanistan - was a coup plotter.
Yeni Safak newspaper, considered close to President Recep Tayyip Erdogan, claimed, in a piece entitled "US Commander Campbell: The man behind the failed coup in Turkey," that the general ran 2 billion dollars through a Nigerian bank account to fund the putsch.
"He's a personal friend and I happen to know that right now he's doing a lot of things and one of them is not planning a coup inside of Turkey," General Joseph F. Dunford said on Monday at a press conference with US Defence Secretary Ash Carter.
"I really don't know where that report could have come from," Dunford added.
Turkey contributes soldiers to US-led efforts in Afghanistan, including training missions. The US has a shared airbase in Incirlik, southern Turkey, where it launches missions against Islamic State and also reportedly houses nuclear weapons.
Aaron Stein, a Turkey analyst based in the US, described the series of articles in Yeni Safak attacking Campbell as "shameful craziness."
"Instrumentalization of anti-Americanism to deflect criticism post-coup attempt has been masterful. Incredibly damaging - but successful," he wrote on Twitter.