Iraqi police allowed dozens of assailants to beat and stab peaceful protesters in Baghdad on February 21, 2011, Human Rights Watch said on Thursday . Security forces have an obligation to protect the right to assemble peacefully and to use only the minimum necessary force to protect lives if violence erupts, Human Rights Watch said. In the early hours of February 21 dozens of men, some wielding knives and clubs, attacked about 50 protesters who had set up two tents in Baghdad's Tahrir Square. The assailants stabbed and beat at least 20 of the protesters who were intending to camp in the square until February 25, when groups have called for national protests similar to the “Day of Anger” in Egypt. The attack came directly after the police had withdrawn from the square, and witnesses suggested the assailants were in discussion with the police before they attacked. “Promises by Prime Minister Nuri al-Maliki to allow protests are meaningless when we see vicious attacks like the one on February 21,” said Joe Stork, deputy Middle East director at Human Rights Watch. “Iraqi authorities should hold police who allowed this attack to happen accountable.” Scores of demonstrations have taken place across the country since early February, mainly focused on the chronic lack of basic services and perceived widespread corruption. Since February 16, security forces have killed at least five protesters and injured more than 100 at demonstrations throughout Iraq. Armed men have also targeted opposition groups and media. In Sulaimaniya, assailants set fire to multiple buildings of the opposition Goran (“change”) party and the headquarters of a newly established TV and radio station that broadcast video of the protests. Protests in Baghdad Shortly after 1 a.m. on February 21 police vehicles on duty at Tahrir Square, in the center of Baghdad, suddenly vacated the area, a dozen witnesses told Human Rights Watch. Immediately afterward, four military Humvees parked on a distant side of the square, while several black SUVs pulled up and parked on an adjoining street. A standing curfew bans all civilian vehicular traffic on Baghdad's roads between midnight and 5 a.m., and vehicles in the Tahrir Square area encounter numerous military checkpoints and patrols. After the vehicles arrived, streetlights surrounding the square went out, and the people in the Humvees turned on floodlights attached to their vehicles. One protest organizer told Human Right Watch that dozens of men wearing civilian shirts, but all with similar dark-colored military-style pants, quickly approached the sleeping protesters, many brandishing knives, batons, and stun-guns, and fanned out around the tents. One asked the organizer if he had a permit for the demonstration, and began to interrogate him. Another witness said a surprised policeman from a nearby checkpoint approached the square with his gun drawn, but when one of the armed men whispered something in his ear, the policeman quickly nodded and withdrew. “At that point, one of them gave a signal, and they all started beating us and running into the tents,” said the witness, who asked not to be named for safety reasons. “I heard people screaming in pain, so I yelled out for everyone to run.” A protester bearing stab wounds, now in hiding, told Human Rights Watch: “I woke up with the pain of the knife sticking in me and everyone yelling. The man who stabbed me told me that I wasn't supposed to be in the square, and that I had to leave, or he would stab me again. He then hit me in the head. I got up as best as I could, and other protesters helped me run away.” Another protester with large bruises on his back and a long laceration on the side of his left leg told Human Rights Watch, “They were punching and stabbing us as we were trying to run from them.” Other witnesses gave consistent accounts of the attack. They said they believed the violence was meant to frighten and disperse the protesters rather than to kill them, although they were all shocked at the brutality of the attack. Various protesters who had encountered police at checkpoints while fleeing into the alleys of the adjoining Betuine neighborhood said the police told them they “were not allowed to intervene.” One protester said a policeman told him they were powerless because the assailants were “from the Office of the Commander-in-Chief of the Armed Forces.” Human Rights Watch observed lacerations or bruises on seven protesters. Witnesses' testimony was also consistent with video viewed by Human Rights Watch, shot at the scene in the hours before the attack, and then of wounded protesters the next morning. At earlier protests in Tahrir Square, Human Rights Watch observed Iraqi security forces intimidating peaceful protesters by filming them and threatening to arrest them, and in one instance saying, “Now, we know who you are.” On February 11 and 13 security forces filmed the faces of participants who were chanting peacefully and told them they would be arrested. On February 23 Human Rights Watch also saw security forces preventing Iraqi journalists from filming or taking photos of the protests. HRW