By Ayla Jean Yackley

ISTANBUL (Reuters) - Turkish authorities ordered the detention of nearly 200 people, including leading businessmen, and seized their assets as an investigation into suspects in last month's failed military rebellion shifted to the private sector.

President Tayyip Erdogan has vowed to choke off businesses linked to U.S.-based Muslim cleric Fethullah Gulen, whom he blames for the July 15 coup attempt, describing his schools, firms and charities as "nests of terrorism."

Tens of thousands of troops, civil servants, judges and officials have been detained or dismissed in a massive purge that Western allies worry Erdogan is using to crack down on broader dissent, risking stability in the NATO partner.

In dawn raids on Thursday, police from a financial-crimes unit entered some 200 homes and workplaces after a chief prosecutor issued 187 arrest warrants, state-run Anadolu news agency said. TV channel CNN Turk said 60 people were detained.

Gulen, formerly close to Erdogan and living in self-imposed exile in Pennsylvania, has denounced the attempted coup, when rogue troops commandeered tanks and jets to attack government installations. He has denied any responsibility.

Police in Istanbul and 17 other provinces were searching for supporters of Gulen's movement, including prominent businessmen, suspected of belonging to and financing his organization, CNN Turk said. The Istanbul prosecutor demanded the assets of the 187 suspects be confiscated, Anadolu said.

Turkey classified Gulen's movement, which espouses philanthropy, interfaith dialogue and science-based education, as a terrorist network in July 2015. It says Gulen's followers spent four decades infiltrating the bureaucracy and security forces in a bid to eventually take control of the state.


Among the businesses targeted were two Fortune 500 companies, CNN Turk said, naming clothing makers Aydinli Group and Eroglu Holding, which both run large retail chains.

No one answered calls to Aydinli, which had sales of 928 million lira ($317 million) in 2015, nor to Eroglu, which reported revenue of 490 million lira last year.

Eroglu said it had no links to any company providing finance to Gulen's movement, according to the Hurriyet news website.

Nejat Gullu, chairman of baklava maker Gulluoglu, was detained, his company said in a statement on its website.

Gullu "would never stand with a terrorist organization or civic group that supports a terrorist organization," it said and expressed confidence he would be cleared of any charges.

Earlier this week, police searched the offices of a nationwide retail chain and a healthcare and technology company, and detained key executives.

Turkey authorities said 4,262 companies and institutions with links to Gulen had been shut. In total, 40,029 people had been detained since the coup attempt, and about half had been formally arrested pending charges.

In purges of the military, police and civil service 79,900 people had been removed from public duty.

Turkey also wants other nations to crack down on Gulen-affiliated organisations, including schools and businesses.

European Affairs Minister Omer Celik called on Germany to shut businesses that have links to Gulen and are operating there, according to Wirtschaftswoche magazine.

The EU and the United States have expressed concern about the scale of the crackdown, and human rights groups have said a lack of due process will ensnare innocent people who had no role in the abortive coup.

But officials say they have to act fast to prevent further attempts by Gulen's "parallel state" to destabilize the government from within the bureaucracy and business community.

It has demanded Washington extradite Gulen so he can face charges in Turkey, drawing a cautious reaction from U.S. officials who say they need to see clear evidence linking Gulen to the military putsch.

A faction of the military attempted to seize power on July 15, killing some 240 people, mostly civilians, and wounding 2,000. About 100 people backing the coup were also killed, according to official estimates.

Authorities are still searching for 137 fugitives, including nine generals and admirals, Defence Minister Fikri Isik told Anadolu. He also said the government is considering an extraordinary meeting of the Supreme Military Council this month as it plans an overhaul of the military to expand civilian control over Turkey's armed forces, which have toppled three governments since 1960.

(Additional reporting by Daren Butler; Writing by Ayla Jean Yackley; Editing by Patrick Markey and Anna Willard)