Counterterrorism police in Istanbul captured 21 foreign Daesh suspects on Friday in multiple operations. Police officers raided 15 locations in the city's 12 districts in the early hours to capture suspects who were allegedly planning to carry out attacks in the city.

Daesh is responsible for several attacks in Istanbul as well as other cities. In June 2016, three Daesh militants killed 45 people in an armed attack followed by suicide bombings at the city's Atatürk Airport. Last year, during New Year's celebrations, a Daesh militant killed 39 people at a popular nightclub on the Bosporus shore. The militant was captured alive in Istanbul's Esenyurt district a few weeks later.

Amid fears that Daesh militants who fled Syria could hit Europe and Turkey, authorities have heightened crackdowns on the terrorist group with almost daily operations.

Though Daesh lost a number of its strongholds in Iraq and Syria, a controversial deal, between Daesh and Syrian terrorist groups linked to the PKK that carry out attacks against Turkey, facilitated their safe evacuation from Raqqa, Syria.

Turkey shares a lengthy border with war-torn Syria and struggles to keep safe from infiltration, despite a giant border wall that is currently under construction. The country is at the forefront of efforts to quell threats from the terrorist group, which partly depends on foreign recruits for fighters.

Turkey has stopped thousands of people from trying to enter Syria to join the group over the past few years. It is now concerned with militants fleeing Iraq and Syria following the fall of the terrorist group. The country has so far stopped more than 5,800 foreign Daesh recruits on its borders and arrested some 10,000 members of the terrorist group in continuous operations.

Last Monday, authorities captured four Iraqi Daesh militants plotting an attack on the U.S. Embassy in Ankara as they were heading to the capital from northern city of Samsun. Two days later, 13 other suspects were captured in the southern city of Adana as the police thwarted a Daesh plot to attack the U.S. consulate in the city.