Police anti-terror raids against suspected IS militants in Turkey
Anti-terrorist teams swooped in on seven addresses connected to a suspect - identified only by the initials K.T. - who is accused of housing suspected IS fighters, late Friday night.
Fifteen of the suspects held in the Istanbul district of Zeytinburnu were foreign nationals who would be deported, police said.
The Istanbul raids come as a number of suspected militants were either arrested or remanded to stand trial on anti-terror charges elsewhere in Turkey.
Five suspected IS members have been remanded in custody by an Ankara court.
In the south-eastern providence of Gaziantep, three suspected people were also held on Friday, the local governorship told the Anadolu news agency in a statement.
The suspects were allegedly planning suicide attacks which would have targeted Turkish soldiers set to join Operation Euphrates Shield in northern Syria, Gaziantep governorship said.
Earlier on Friday, police in Turkey's northern Samsun province detained three Iraqi nationals - believed to be brothers - on terror charges.
The three men were later transferred to Sakarya province in western Turkey, according to sources who spoke on condition of anonymity.
The brothers were charged with being members of an armed terrorist organisation and are also accused of making bombs.
Turkey has taken steps to crack down on IS since 2014 when the hardline group launched a series of suicide bombings in the country.
IS also claimed responsibility for the New Year's nightclub attack in Istanbul which killed 39 people.
Turkey is pressing on with Operation Euphrates Shield in norther Syria, which began late August 2016 in support of pro-Ankara Syrian rebels.
The aim has been to oust IS fighters - as well as Kurdish militias - from the border area.