Turkish authorities detained 82 foreigners planning to go to Syria and suspected of links to IS in a string of anti-terror raids in Istanbul, state media reported on Friday.
The suspects had previously been involved with Islamic State group extremists in "conflict zones", state-run news agency Anadolu said without giving further detail.
They were detained during raids on 14 addresses and were planning to go to Syria "in the coming days", it added.
Elsewhere in the southern city of Adana, 11 alleged IS members of Syrian origin were detained, the agency said in the same report.
The detentions come a day after vast anti-IS raids in Ankara during which 173 people were detained over alleged terror links.
A total of 1,500 police officers took part in the raids after authorities issued arrest warrants for 245 suspects.
According to the interior ministry, around 450 suspects were detained accused of helping or being in contact with IS in October.
Turkey has suffered a series of terror attacks blamed on IS over the past two years, including one on a popular Istanbul nightclub celebrating New Year during which 39 people were killed by an IS gunman.
Uzbekistan-born Abdulgadir Masharipov previously confessed to the 2017 attack and will go on trial in Istanbul on December 11.
Turkey came under attack from IS from late 2015 onwards after Ankara allowed the US military to conduct air strikes on IS targets in Syria via Turkey's southern Incirlik air base from August 2015.