Turkish Interior Minister Suleyman Soylu announced Turkey has captured an "important" figure within the ISIS group in Syria.
Soylu said on Wednesday that the suspect is still being interrogated but did not name the figure or provide further details.
Turkey has said it captured and detained several members of the family of the slain ISIS group leader, Abu Bakr al-Baghdadi, including one of his wives, his sister and a daughter.
Baghdadi blew himself up during an October 26 raid by US special forces on his heavily fortified safe house in the Syrian province of Idlib.
Separately, Soylu said Germany and the Netherlands had agreed to take back German and Dutch ISIS detainees and their families from Turkey, after Ankara started to repatriate the fighters this week.
On Monday, Turkey said it had deported two of the detainees, a German and an American, and added that it will deport another 23 European nationals in the coming days.
Turkey holds hundreds of ISIS suspects in its jails and says it has captured another 287 during its military offensive in northeast Syria against Kurdish People’s Protection Units (YPG) fighters – an incursion which has further strained ties with its NATO allies.
"We have our own policy and we are implementing it without compromise. Those who want to step out of our way will, but those who don't will face the consequences," Soylu said in the southeastern province of Van on Wednesday.
"I would like to especially thank two countries here. One is Germany and the other the Netherlands," he added. "As of last night, they have confirmed that they will take back terrorists from ISIS who are citizens of their countries and their wives, children and all the others," he said.
Turkey has said it will deport the detainees to Ireland, Germany, France and Denmark.
French Interior Minister Christophe Castaner said on Tuesday that France would take back 11 suspected ISIS members from Turkey.
Ireland's Foreign Minister Simon Coveney also said that two Irish nationals set to be deported from Turkey had the right to return to Ireland.
On Monday, Greek police said that Turkish police came to the border post at the Greek town of Kasanies and requested that one of the detainees, a US citizen of Arab descent, be admitted to Greece as he had been arrested for exceeding his stay in Turkey.
Greek police said that a check carried out in a database of Greek and cooperating countries did not find anything against him, and that the man has been refused entry to Greece and sent back to Turkey. Turkish state media said on Wednesday he was in the buffer zone between Turkey and Greece.
Turkey's offensive against the YPG, US partners in the battle against ISIS in Syria, prompted concern that the detained extremists could break out and regroup amid the chaos.
Washington says that nearly all the 10,000 ISIS suspects held by the SDF in Syria remain in captivity, but a senior US State Department official described them on Tuesday as a "ticking time-bomb" and urged states to take back their citizens.