Turkish President Recep Tayyip Erdogan gas told his foreign minister to expel the ambassadors of 10 countries, including France, Germany and the United States, who had appealed for the release of a jailed civil society leader.
The envoys issued a highly unusual joint statement last Monday saying the continued detention of Parisian-born philanthropist and activist Osman Kavala "cast a shadow" over Turkey.
In a joint statement, the ambassadors of Canada, Denmark, France, Germany, the Netherlands, Norway, Sweden, Finland, New Zealand and the United States called for a just and speedy resolution to Kavala's case, and for his "urgent release".
Seven of the ambassadors represent Turkey's NATO allies.
The escalating row with the Western countries -- most of which are also NATO allies -- caps a torrid week for Turkey in which it was added to a global money-laundering and terrorism-financing blacklist and its currency plunged over fears of economic mismanagement and the risk of hyperinflation.
"I have ordered our foreign minister to declare these 10 ambassadors as persona non grata as soon as possible," Erdogan said, using a diplomatic term meaning the first step before expulsion.
"They must leave here the day they no longer know Turkey," he said, accusing them of "indecency".
Several European countries said late on Saturday they had received no official notification from Turkey.
"We are currently in intensive consultation with the nine other countries concerned," the German Foreign Ministry said.
"Our ambassador has not done anything that would justify the expulsion," Norwegian foreign ministry spokeswoman Trude Maseide told media in her home country.
She vowed to continue pressing Turkey on human rights and democracy -- comments echoed by Danish and Dutch officials.
The United States was aware of the reports and was seeking clarity from the Turkish Ministry of Foreign Affairs, a State Department spokesperson said.
Kavala, 64, has been in jail without a conviction since 2017 on charges linked to 2013 anti-government protests and a failed military coup in 2016.
The Western ambassadors had called for a "just and speedy resolution" to his case.
But on Saturday, Erdogan described Kavala as the "agent in Turkey" of Hungary-born American billionaire George Soros -- a regular target of right-wing and anti-Semitic conspiracy theories.
Kavala's supporters see him as a symbol of the sweeping crackdown Erdogan unleashed after surviving a 2016 coup attempt.
Kavala told French news agency AFP from his cell last week that Erdogan was trying to blame foreign conspiracy for opposition to his almost two-decade rule, particularly the 2013 nationwide protests sparked by plans to demolish Gezi park in Istanbul.
"Since I am accused of being a part of this conspiracy allegedly organised by foreign powers, my release would weaken the fiction," he said.
Kavala was acquitted of charges linked with the Gezi protests last year only to be re-arrested before he could return home over alleged links to the 2016 coup plot.
Human rights watchdog the Council of Europe has issued a final warning to Turkey to comply with a 2019 European Court of Human Rights order to release Kavala pending trial.
If it fails, Turkey could eventually have its voting rights or even its membership suspended.
Erdogan faces multiple challenges at home and abroad, with global financial misconduct watchdog FATF placing Turkey under surveillance for failing to properly combat money laundering and terrorism financing.
Erdogan passed anti-terror laws but they failed to impress FATF and critics said the new rules mostly targeted Turkish NGOs that promote pro-Kurdish causes and human rights.
The president's attacks on Kavala this week caused jitters in the markets with fears of a deepening confrontation with the West sending the lira slumping even further against the dollar.
Erdogan is in danger of "dragging the Turkish economy into a president-made crisis", Eurasia Group said.
He has said previously that he plans to meet US President Joe Biden at a summit of the Group of 20 (G20) major economies in Rome next weekend.