CAIRO, Jan 28 (Aswat Masriya) - Six rights groups said the January 2011 uprising anniversary saw the "excessive use of lethal force by security forces against protesters," in a joint statement on Wednesday.

The rights groups, which include the Arab Network for Human Rights Information and the Cairo Institute for Human Rights Studies, expressed "grave condemnation" of the "extrajudicial killings carried out by security forces" before and during the anniversary of the January 2011 uprising.

They called for the start of an "extensive investigation" into all incidents of protester killings since the uprising.  

The joint statement comes days after the passing of four years since the uprising. The anniversary, marked on Sunday was marred by deadly violence, which left at least 23 dead, according to official figures.

The deadliest of the violence took place in the east Cairo neighbourhood of Matariya. The joint statement cited eyewitnesses as saying that when people marched onto Matariya, "security forces assaulted them". This drove some of them to stage a sit-in, "which was met by lethal force from security forces," the statement read.

Interior Minister Mohamed Ibrahim visited Matariya on Tuesday night to inspect security conditions. On Monday, he had accused the Brotherhood of being responsible for the violence across the nation during a press conference.

The rights groups called for holding the police accountable for violating Egypt's protest law. The controversial law, issued in November 2013, stipulates that the police must use "gradual force" while dispersing illegal gatherings.

Human Rights Watch said there is a need in Egypt "for an independent investigation into the authorities’ excessive use of force," in a statement on Monday.   

The violence in Egypt was condemned by the United States, United Kingdom and most recently, the United Nations. Egypt's Foreign Ministry responded to the condemnations with criticism.