Security forces captured five suspected DAESH terrorists, including one foreign national, during two separate operations in southeastern Kilis province on Wednesday, the provincial governor's office said in a statement Thursday.

According to the statement, the Turkish military nabbed four suspects with Turkish citizenship as they attempted to cross the Turkish-Syrian border, and a court has detained them.

An investigation is ongoing into the foreign national, the statement added.

Also on Thursday, Istanbul and İzmir police conducted anti-terror operations following the terrorist attack on Atatürk Airport that took place on Tuesday, and security forces killed two suspected DAESH terrorists trying to illegally cross the border from Syria who ignored repeated warnings to stop.

Police in Istanbul and İzmir conducted a series of raids on Thursday in various parts of the city and detained at least 20 suspects. The nationality of the suicide bombers was also revealed on Thursday with reports identifying one of the suicide bombers as from Dagestan in Russia, while the others were from Uzbekistan and Kyrgyzstan.

According to Anadolu Agency, police raided 16 addresses in Istanbul's Pendik and Sultanbeyli districts on the Asian side of the city and the Başakşehir district on the European side and detained 13 suspects, four of whom are reportedly foreign nationals.

In the Aegean coastal city of İzmir, police detained at least nine suspects.

Meanwhile, Turkish security forces killed two suspected DAESH terrorists on the border with Syria when they tried to illegally cross into Turkey and ignored warnings to stop. According to security sources, the suspects were Syrians in contact with DAESH supporters Abu Ali and Mustafa Demir. One of them was identified as Muhammad Arab, wanted by Turkey and listed in intelligence reports as a suspect capable of carrying out suicide attacks in the capital Ankara and southern Adana province.

Turkey strengthened security measures throughout the country following the deadly shooting and triple suicide attacks on Istanbul's Atatürk Airport on June 28.