US consulates in Turkey indefinitely halted all non-immigrant visa services on Sunday, the American embassy said, after one of the mission's Turkish staffers was arrested in the latest dispute between the Nato allies.

The embassy said “recent events” had forced the US government to reassess Turkey's “commitment” to the security of US mission services and personnel in the country.

In order to minimise the number of visitors while the assessment is carried out, “effective immediately we have suspended all non-immigrant visa services at all US diplomatic facilities in Turkey,” it said.

Non-immigrant visas are issued to all those travelling to the United States for tourism, medical treatment, business, temporary work or study. Visa services are only those seeking to live in the US permanently.

Beyond mentioning “recent events”, the statement made no explicit mention of the arrest by Turkish authorities of a local Turkish staffer working at the US consulate in Istanbul.

The employee was remanded in custody by an Istanbul court late Wednesday on accusations of links to the group of US-based preacher Fethullah Gulen, blamed by Ankara for last year's failed coup against President Recep Tayyip Erdogan.

The man has been formally charged with espionage and seeking to overthrow the Turkish government. The embassy on Thursday said it was “deeply disturbed” over the arrest and rejected the allegations as “wholly without merit”.

The statement also condemned leaks in the local press which it said came from Turkish government sources that were “seemingly aimed at trying the employee in the media rather than a court of law.”

But Erdogan's spokesman Ibrahim Kalin has defended the arrest, saying “there must be serious evidence” and pointing to a phone call made from the Istanbul consulate to a key suspect on the night of the coup.

The issue has added yet another bone of contention in the increasingly troubled relationship between Washington and Ankara.

Turkish officials had expressed hope of a new page in Ankara-Washington relations under President Donald Trump.

Turkey has pressed Washington for the extradition of the Pennsylvania-based Gulen, who denies any link to the coup bid.

The lack of movement on the issue has further strained ties already fraying over Washington's support for a Syrian Kurdish militia Ankara deems to be a terror group.

Meanwhile, members of Erdogan's security detail were indicted by US authorities after clashes with protesters during an official visit this year, infuriating the Turkish president.

American pastor Andrew Brunson, who ran a church in the western city of Izmir, has been held by Turkish authorities since October 2016 on charges of being a member of Gulen's group.

Erdogan suggested last month that Turkey could release him in exchange for Gulen but Washington showed little interest in the proposal.