Turkey’s President Recep Tayyip Erdogan has extended the period in which suspects can be detained without charge to 30 days, an official statement says.
The statement also ordered the closure of more than 1,000 private schools and more than 1,200 associations.
It follows last week’s failed coup attempt against Mr Erdogan and the subsequent declaration of a state of emergency.
Mr Erdogan has blamed the coup attempt on US-based cleric Fethullah Gulen.
Mr Gulen, who went into exile after he fell out with Mr Erdogan, has denied any involvement.
The Turkish leader has said the state of emergency will allow the authorities to restore order and deal with the aftermath of the failed coup effectively.
At least 60,000 state employees have been detained or suspended in an internationally criticised purge.
Education ministry officials, private school teachers and university heads of faculty together account for more than half the people targeted.
The schools and associations whose closures have now been ordered are suspected of having links to Mr Gulen, Turkey’s state news agency Anadolu said.
Other institutions ordered to be shut down included 19 trade unions, 15 universities and 35 medical institutes, the agency said.
Also on Saturday, Ankara’s chief prosecutor Harun Kodalak was reported by Turkish media as saying 1,200 soldiers detained in the wake of the coup had been released.
Those freed were said to be low-ranking soldiers. Thousands of other service personnel, including more than 100 generals and admirals, remain in detention.
The state of emergency allows the president and cabinet to bypass parliament when drafting new laws and to restrict or suspend rights and freedoms.
Imposition of the measures has been criticised by France and Germany, as well as top EU officials, but Turkey has defended its actions, saying only those “100% identified” with those behind the coup are being targeted.
Mr Erdogan told France 24 television on Saturday that the EU was “biased and prejudiced” against Turkey.
Human rights groups including Amnesty International had warned Turkey against extending the period allowed for detention without charge, which previously stood at a maximum of four days.
Amnesty has said Mr Erdogan is going “well beyond what might be considered a legitimate response to the coup attempt”.
Other critics have accused him of consolidating power on a scale largely unprecedented since Turkey’s first democratic elections in 1946.