By Daren Butler and Tuvan Gumrukcu
ISTANBUL (Reuters) - Turkish police searched the offices of a nationwide retail chain and a healthcare and technology company on Tuesday, arresting dozens of people in some of the biggest raids on private businesses since last month's failed coup.
More than 35,000 people have been detained in a massive purge since the July 15 attempted putsch, when a group of rogue soldiers commandeered tanks, warplanes and helicopters in an attempt to overthrow the government.
Around half of those detained have been placed under formal arrest and tens of thousands more have been suspended in the military, police and civil service. The breadth of the probe has worried the West, which fears President Tayyip Erdogan is using it to quash dissent.
Private businesses have also been targeted in what the government describes as a crackdown on followers of Fethullah Gulen, a cleric based in self-imposed exile in the United States, who is blamed by Turkey for the coup.
Police targeted discount supermarket chain A101 and healthcare and technology group Akfa Holdings, on suspicion they gave financial support to Gulen's network, state-run Anadolu Agency said.
Gulen denies involvement in the coup. Washington says it will extradite him to Turkey only if presented with firm evidence. Turkey's foreign minister spoke to U.S. Secretary of State John Kerry on Tuesday about Gulen's extradition, foreign ministry sources said. Kerry is due to visit Turkey this month.
A101, which operates thousands of stores across Turkey, said financial crimes police searched its Istanbul headquarters for six hours on Tuesday morning. It had cooperated with police and its businesses continued to operate, the company said.
A101 said it had no "corporate, financial or trade links" to any illegal group, although it acknowledged that now-defunct Islamic lender Bank Asya had once been a shareholder. The bank was founded by Gulen's followers and later seized by regulators, and is now being wound down.
Private news agency Dogan said police detained A101's chairman, Turgut Aydin, at his home in the eastern Black Sea province of Trabzon. Aydin and his family are also majority owners of the Memorial hospitals group. Some 36,000 people work for his companies.
Anadolu said 50 people were detained in the separate raid at Akfa, including the company's chairman. No one was immediately available for comment at Akfa.
Police also searched offices at the main courthouse on the Asian side of Istanbul, according to a courthouse employee, a day after major raids on three courthouses on the European side of the city, which sits on the strait dividing the continents.
"Police are currently in the courthouse. They came in with a list of names. The names were of those who were ordered to be taken into custody, and they are searching the building," the employee told Reuters, declining to be identified.
Police had detention warrants for 83 people at the court, Anadolu reported. A day earlier police detained at least 136 court staff in the raids on courts on the European side of the city.
Erdogan accuses Gulen of harnessing an extensive network of schools, charities and businesses, built up in Turkey and abroad over decades, to infiltrate state institutions and build a "parallel structure" that aimed to take over the country.
Before the failed coup, in which more than 240 people were killed, the authorities had already seized Bank Asya, taken over or closed several media companies and detained businessmen on allegations of funding the cleric's movement.
In a speech to his ruling AK Party deputies in parliament on Tuesday, Prime Minister Binali Yildirim sought to calm public concerns about the purge.
He said it targeted only be those who maintained links to Gulen after Dec. 17, 2013 - the date when police and prosecutors seen as sympathetic to the cleric launched a corruption probe into Erdogan and his inner circle. That event triggered a public rift between Erdogan and Gulen, who had previously been allies.
"Millions of our innocent citizens can relax. If you did not consciously support FETO after Dec. 17, you should not be worried," Yildirim said, using the acronym for "Gulenist Terror Group", as Ankara refers to Gulen's movement. "After Dec. 17 there is no excuse".
The government is also planning to shut down the TIB telecommunications regulator and transfer its powers to its parent, an umbrella regulatory body, Deputy Prime Minister Numan Kurtulmus said this week.
The TIB has previously been targeted in the government crackdown against Gulen. In January 2015, police detained 23 of its employees in an investigation into allegations of illegal wiretapping targeting Erdogan and other top officials.
The government also plans further dismissals in the foreign and interior ministries, as well as the coastguard and military, Kurtulmus said.
(Writing by David Dolan; editing by Patrick Markey and Peter Graff)