A recent footage revealed on Sunday showed the leftist militant group, terrorists of the Revolutionary People's Liberation Party-Front (DHKP-C) terrorists are leftist militant group raiding a coffee house in Istanbul's Okmeydanı district to threaten people inside against supporting "Yes" vote in the upcoming referendum.

The footage showed two armed and masked terrorists carrying guns, who called themselves "the front militias", telling people in the coffee house that anyone who is promoting the "Yes" vote, supporting the Justice and Development Party (AK Party) or President Recep Tayyip Erdoğan would be punished.

The DHKP-C, although less influential in Turkey than other terrorist organizations like the PKK, still represents a considerable threat to the country with a string of attacks over recent years.

The group was behind a suicide bombing that targeted the American Embassy in Ankara in 2013, leaving a Turkish security guard dead. The group and it was also the culprit in the killing of a prosecutor in a courthouse complex in Istanbul back in March 2015. The group is also responsible of 2015 killing of Istanbul prosecutor Mehmet Selim Kiraz hours after he was taken hostage.

On April 16, 55.3 million Turkish people are expected to cast their votes in constitutional amendments that have been on the agenda since Erdoğan's election as president in August 2014.

The changes will abolish the post of prime minister, which the AK Party claims resulted in an ineffective two-headed political system, replacing it with a stronger system, which is expected to produce stability and a more effective governing system in the long term.