Turkish authorities on Thursday launched dawn raids in Istanbul and the southern city of Mersin to arrest suspected members of an ultra-left group, a day after two of its militants attacked the Dolmabahce Palace in Istanbul.

Turkish authorities on Thursday launched dawn raids in Istanbul and the southern city of Mersin to arrest suspected members of an ultra-left group, a day after two of its militants attacked the Dolmabahce Palace in Istanbul, state media said.

Police detained over 40 suspected militants from the Marxist Revolutionary People's Liberation Party Front (DHKP-C) in Istanbul's Sariyer district on the shores of Bosphorus and several districts of Mersin, Anatolia news agency reported.

The majority of the detentions took place in Mersin, where the suspected militants from other parts of Turkey had been staying in tents on a beach in the port city, it added.  

Police on Wednesday detained two militants over the armed attack on guards outside the Dolmabahce Palace, one of Turkey's main tourist attractions which also houses offices of the prime minister. No fatalities were reported.

The DHKP-C on Thursday claimed responsibility for the attack on their website.
"We will break the hands raised against the peoples' fighters who ensured justice by attacking the Dolmabahce Palace," it said.

The DHKP-C has claimed a string of attacks in Turkey in recent months, including a similar attack on the Dolmabahce Palace on January 1 where two grenades were hurled at the guards, which failed to explode.

The DHKP-C, known until the mid-1990s as Devrimci Sol (Revolutionary Left), is a deeply secretive group which goes quiet for periods before re-emerging to stage attacks.

Mainly active in Istanbul, it seeks a Marxist revolution in Turkey but also espouses a fiercely anti-Western and anti-NATO agenda.
The group had claimed a 2013 suicide attack at the US embassy in Ankara that left a security guard dead.

Turkey has been on heightened alert since Ankara launched a two-pronged offensive to bomb militants of Takfiri group, ISIL (so-called Islamic State in Iraq and Levant) in Syria and Kurdish rebels in northern Iraq and southeastern Turkey following a series of deadly attacks.

According to the government, more than 2,500 people have so far been detained in raids targeting suspected members of the Kurdistan Workers' Party (PKK), ISIL and DHKP-C, the overwhelming majority of them from the PKK.

Turkey had been before reluctant to step up fight against ISIL. Media reports repeatedly said that Ankara has been aiding ISIL terrorists against the Kurdish fighters and against the Syrian government.

However, deadly attacks blamed on ISIL recently rocked Turkey, prompting Ankara to allegedly step the fight against the Takfri group.

But, so far, the air strikes have overwhelmingly concentrated on the separatist Kurdish rebels.