The number of suspects detained in the aftermath of a terror attack in Istanbul by the Revolutionary People’s Liberation Party-Front (DHKP-C) rose to 90 as of Wednesday. Two assailants were shot dead when they fired upon police officers at a security checkpoint outside the massive courthouse complex in the Çağlayan neighborhood on Istanbul’s European side. A female passerby was killed in the attack while several, including police officers, were injured.

Media reports say terrorists identified as S.Y. and P.B. were planning to broadcast their attack live if they managed to enter the courthouse. They were stopped at the checkpoint, however, when police were suspicious of them and sought to search the duo. Security camera footage emerged after the attack showed the assailants producing weapons in front of the checkpoint and indiscriminately firing. The attack took place as P.B.’s sister was standing trial inside the courthouse on terror charges. The broadcaster A Haber reported on Tuesday that a search of two assailants found one of them had a device attached to a cellphone for a live broadcast of their actions. One of them was also wearing a T-shirt with a slogan of a terrorist group. News agencies said 48 bullets, a large number of plastic handcuffs and pepper spray were also found in possession of the terrorists.

Interior Minister Ali Yerlikaya had initially announced that 40 people were arrested in connection with the attack in the immediate aftermath of the shooting.

Both assailants served time on charges of membership of a terrorist group in the past but they were apparently not involved in any acts of terrorism before. E.Y. was most recently sentenced to seven years and six months in prison eight months ago but appealed the ruling. He was released with a travel ban and judiciary control. P.B. was questioned by police in the past on suspicion of DHKP-C membership and was recently released from prison. Media outlets reported that P.B. complained of prison conditions and her letters were repeatedly made public by a lawmaker of a party associated with the PKK, another terrorist group whose ideology is similar to the DHKP-C.

The DHKP-C was at the forefront when the notorious Gezi Park protests of 2013 escalated into deadly riots, and members of the group participated in the riots. Some suspects imprisoned for links to the terrorist group have drawn support for their release by lawmakers of the main opposition Republican People’s Party (CHP). A CHP lawmaker was among those calling for the release of E.Y. when the latter was imprisoned. "Yesterday’s attack proved once more that the CHP is the staunch defender of those terrorists. Some CHP lawmakers even filed a motion in Parliament (for the improvement of prison conditions for terrorists). The CHP is a friend of the political wing of the terrorist group," Erdoğan said in a speech in the southeastern province of Şanlıurfa on Wednesday.

The DHKP-C is listed as a terrorist organization by Türkiye, the United States and the European Union. The terrorist group pursues a far-left ideology and has been actively carrying out attacks and assassinations in the country since the 1980s, but its campaign of violence hit a snag when faced with Türkiye’s barrage of counterterrorism operations. The DHKP-C’s most high-profile attacks include a suicide bombing that targeted the U.S. Embassy in the capital Ankara in 2013 and the killing of prosecutor Mehmet Selim Kiraz. It was also responsible for the assassination of Özdemir Sabancı, a tycoon who was a member of the prominent business dynasty, Sabancı, in 1996.

The group has become less active in the country in recent years but remains a major security threat. The DHKP-C, which operated under the name "Dev Sol" until 1994, claimed responsibility for a series of high-profile murders, including the assassination of nationalist politician Gün Sazak and former Prime Minister Nihat Erim in 1980. The group also killed several Turkish intelligence officers. In 1994, the DHKP-C was founded after Dev Sol splintered.

The group's terror activities remained relatively minor compared to the PKK, another terrorist group targeting Türkiye. The DHKP-C attempted to stage a bloody comeback in recent years by carrying out attacks against the police. In 2012, about 10 years after its last known lethal attack in Türkiye, the DHKP-C conducted a suicide bombing at a police station in Istanbul, killing a police officer. After the February 2013 attack on the U.S. Embassy, it launched rocket attacks against the Ministry of Justice in Ankara and the headquarters of the ruling Justice and Development Party (AK Party) in March 2013. In September 2013, the DHKP-C claimed responsibility for a rocket attack against the headquarters of the Turkish police in the capital. No casualties were reported in the three attacks. In 2015, DHKP-C members took hostage prosecutor Mehmet Selim Kiraz and published photos of the captive prosecutor through social media accounts associated with the terrorist group. Kiraz was killed by the terrorists hours later before police eliminated the hostage-takers. The courthouse in Çağlayan officially bears Kiraz's name.

Türkiye has begun to emerge from a violent spell that started a decade ago when it was hit by repeated bombings and other attacks linked to Daesh and the PKK. Although those attacks have largely died down thanks to counterterrorism operations, both Istanbul and the capital Ankara remain on high alert.

Last month, one man was shot dead by two gunmen who opened fire inside a Catholic church in Istanbul. The attack was blamed on Daesh and authorities captured a large number of Daesh suspects following the attack.

In October, two assailants injured two police officers in an attack on the government district in the capital Ankara that was claimed by the PKK. Türkiye responded by stepping up airstrikes against PKK targets in Syria and Iraq.