At least 40 members of an ultra-left wing group have been detained in Turkey following an armed attack Wednesday on guards outside a historic Istanbul palace, Turkish news outlets reported Thursday. The attack comes amid a string of bombings by left-wing militant groups that have targeted soldiers in Turkey's restive southeast, predominantly-Kurdish region.

Suspected militants detained Thursday were reportedly from the Marxist Revolutionary People's Liberation Party Front, or DHKP-C, a group Turkey has classified as a terrorist organization that has been responsible for suicide bombings and assassinations throughout the country. A majority of the detentions occurred in the southeastern city of Mersin, where suspected militants from other parts of Turkey were reportedly staying, though there were also arrests made in Istanbul, Agence France Presse reported.

The crackdown was launched a day after Turkish police detained two militants for an armed attack on security outside the Dolmabahce Palace, a popular Istanbul tourist attraction that also houses government offices. DHKP-C claimed responsibility via social media for the attack. There were no reports of fatalities.

The group has also taken responsibility for a series of separate attacks in recent weeks, including an assault on the American consulate in Istanbul. Tensions have swelled since a suicide bomber from the Islamic State group, also known as ISIS or ISIL, targeted left-wing activists in the southern Turkish town of Suruc, killing 31 left-wing activists late July. Left-wing organizations held Turkey accountable for the attack for its failure to halt the spread of ISIS in the country.

At least 2,500 people have been detained so far in raids on suspected ISIS, Kurdish and left-wing militants across the country, according to the government, AFP reported. A majority of those individuals, many of whom have already been released, were from the Kurdistan Workers' Part, a left-wing Kurdish militant organization that fought a decades-long insurgency against the Turkish government with the goal of establishing an autonomous Kurdish state.

Fighting in Syria has derailed much of the progress made between Kurdish militants and the Turkish government in negotiations for a long-term peace in recent years.

In a video released Tuesday, a member of ISIS, now identified as 47-year-old Fatih Acıpayam, called on supporters of the militant group to rise up and conquer Istanbul as the Turkish government has vowed to fight alongside the U.S.-led anti-ISIS coalition.