At least six people were killed in Cairo on Thursday during a protest marking the one year anniversary of the Rabaa massacre.

Protesters gathered in different groups around Cairo to protest on the one year anniversary of the Rabaa massacre, in which 1,000 people were killed while peacefully protesting the military overthrow of ousted President Mohamed Morsi.

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The protesters marched throughout Cairo shouting "we demand retribution," the Middle East Eye reported. They also announced the formation of a left-wing group called the People's Resistance Movement, but it is unclear what the group's aims are and what attachments they may have to other organizations.

Turkish Anadolu Agency reported that six protesters have been killed so far by police, including one that was killed by a shotgun blast.

Police used tear gas and gunfire in an attempt to disperse the crowds.

The protests in Cairo are the biggest of protests that have flared throughout the country on Thursday. Large protests are also taking place in Alexandria and Giza.

Small explosions, including a car exploding in the industrial city of Helwan, were reported by Egyptian news agencies.

A homemade bomb was planted inside a train in Luxor but was defused. Similar devices were found in Ramadan City and in central Cairo.

Security officials said that at least 12 people were injured. More than 60 members of the Muslim Brotherhood, a pro-Morsi organization, have been arrested on charges of rioting and violence.

In a report released on Tuesday, Human Rights Watch said that the Rabaa massacre is one of the worst single day massacres in recent history, and was likely premeditated. The title of the report is "All According to Plan: The Rab'a Massacre and Mass Killings of Protesters in Egypt".

The Middle East Eye reported that though the Egyptian police did not answer calls for comment, they have said in the past that they do not use live ammunition to disperse crowds.

TagsMohamed Morsi, Rabaa massacre, Arab Spring, Cairo protests