ANKARA (Reuters) - A U.S. consulate employee in Istanbul was arrested on charges of links to a cleric blamed for last year’s failed coup, Turkish authorities said on Thursday, a move condemned by Washington as baseless and damaging to ties between the NATO allies.

President Tayyip Erdogan’s spokesman said the locally-recruited consulate worker had been in contact with Adil Oksuz, a theology professor dubbed the “imam of the air force” for his alleged close links to coup plotters high up in the military.

“The arrested U.S. consulate worker was found to have had frequent communication with the FETO suspect Adil Oksuz,” Ibrahim Kalin told reporters, using Erdogan’s acronym for the network of U.S.-based cleric Fethullah Gulen that Erdogan accuses of engineering the coup attempt.

The U.S. Embassy in Ankara said it was deeply disturbed by the arrest of the locally employed staff member.

“Baseless, anonymous allegations against our employees undermine and devalue (the) longstanding partnership” between the United States and Turkey, the embassy said in a statement.

Turkey’s Foreign Ministry said the arrested individual was not on the official list of registered personnel for the U.S. consulate and therefore had no diplomatic or consular immunity.

U.S.-Turkish tensions have risen over U.S. military support for Kurdish YPG fighters in Syria, considered by Ankara to be an extension of the banned PKK which has waged an insurgency for three decades in southeast Turkey.

Turkey has also pressed, so far in vain, for the United States to extradite Gulen over the July 2016 putsch, in which more than 240 people were killed. Gulen denies any involvement.

PARLIAMENT BOMBING

Authorities say Oksuz, the theology professor, helped orchestrate the bombing of parliament by rogue air force pilots during the coup bid. He was detained near an Ankara air base hours after the coup was put down, only to be released by a judge two days later. He has been on the run since.

The state-run Anadolu news agency identified the consulate employee as a male Turkish citizen and said he was arrested late Wednesday on charges of espionage and attempts to damage the constitutional order and Turkey’s government.

Since the coup attempt, more than 50,000 people have been jailed pending trial over alleged links to Gulen, while 150,000 people have been sacked or suspended from jobs in the public and private sectors.

Human rights groups and some of Turkey’s Western allies have voiced concern about the crackdown, fearing Erdogan is using the coup as a pretext to quash dissent.

The government says only such a purge could neutralize the threat represented by Gulen’s network, which it says deeply infiltrated institutions such as the army, schools and courts.

Friction with the United States has also arisen from the indictment last month by a U.S. court of Turkey’s former economy minister Zafer Caglayan.

Caglayan and the ex-head of a state-owned Turkish bank were charged with conspiring to violate U.S. sanctions on Iran by illegally moving hundreds of millions of dollars through the U.S. financial system on Tehran’s behalf.

Turkey says Caglayan acted within international law and that charges against him amounted to a coup attempt through American courts.