Police have detained four Islamic State suspects who were allegedly planning to carry out a "sensational" attack in Turkey and seized 24 suicide attack belts, officials said.
The latest detentions came as CIA chief Mike Pompeo arrived in Turkey to discuss the fight against the extremist group in Syria and Iraq, making his first overseas trip since taking office in the US.
The suspects were put under custody in an anti-terror operation in Gaziantep, near the border with Syria, according to the Gaziantep provincial governor's office.
Police found the suicide belts - made with 150kg of explosives and fortified with metal pieces - as well as two automatic rifles, 14kg of TNT and other materials during the operation, it said.
There were no details on the nationalities of the suspects, who were allegedly taking orders from high-level IS members in Syria.
One suspect was wanted for membership of a terror organisation, according to the governor's office.
Last year, Turkey suffered a series of deadly attacks carried out by IS or Kurdish militants and has stepped up anti-terrorism operations across the country.
Some 750 people with alleged IS links were detained in a major police sweep in 29 Turkish provinces last week.
A Turkish official said Mr Pompeo was to meet with his Turkish counterpart, Hakan Fidan, as well as President Recep Tayyip Erdogan and Prime Minister Binali Yildirim in Ankara.
The talks will include plans for a possible operation to retake the IS stronghold of Raqqa, said the security official.
Mr Pompeo's visit follows a phone call between US President Donald Trump and Mr Erdogan.
Turkey is hoping for a reset in relations with the United States that were strained under the Obama administration over Turkish demands for the extradition of a US-based cleric, Fethullah Gulen, who Turkey has accused of orchestrating a failed coup.
Turkey was also angered by US backing for Syrian Kurdish fighters, since it considers them terrorists because of their links to outlawed Kurdish rebels in Turkey.
Turkey, whose troops are currently trying to liberate the IS-held town of al Bab in Syria, is pressing for a joint operation with the US to recapture Raqqa without the Syrian Kurdish group's involvement.
The security official said that during talks with Mr Pompeo, Turkey would also seek greater US co-operation in Turkey's struggle against Mr Gulen's movement and the Kurdish rebels.