Turkish security forces detained at least 48 suspects Thursday as part of an operation against terrorist groups across Turkey, according to security sources.

An Izmir-based operation was carried out simultaneously across 12 provinces of Turkey as part of a probe against far-left terror groups such as the Marxist-Leninist Communist Party (MLKP), the Turkish Communist Party-Marxist-Leninist (TKP/ML), the Revolutionary Socialist Workers' Movement (DSIH) and the PKK.

Out of the 51 suspects, 48 were arrested during the operations, said the sources, who spoke on condition of anonymity due to restrictions on talking to the media.

The co-chair of the terrorist group the Oppressed Socialist Party (ESP), Özlem Gümüştaş, former Izmir provincial heads Pınar Türk and Kerim Altınmakas, as well as two lawyers and four Izmir municipality personnel were among those arrested.

Anti-terror units seized a number of digital materials, illegal publications, documents belonging to terrorist groups and TL 50,000 (about $6,750) during the operations.

Sources said the operation to find the remaining suspects continues.

The MLKP was founded in 1994 and was added to Turkey's active terror list in 2007.

The terrorist group is responsible for many attacks in Turkey and northern Syria, including the bombing of a public bus in Istanbul in 2004 that killed three civilians.

Founded in 1972 in Turkey, TKP/ML is an outlawed group carrying out illegal activities as well as armed attacks to establish Marxist-Leninist rule in the country. It is listed as a terrorist organization in Turkey.

In its more than 40-year terror campaign against Turkey, the PKK – listed as a terrorist organization by Turkey, the U.S. and the European Union – has been responsible for the deaths of 40,000 people, including women, children and infants.