Cairo - Egyptian police using tear gas dispersed small demonstrations in Cairo by supporters of ousted Islamist president Mohammed Morsi on Friday's second anniversary of the killing of hundreds of protesters by security forces.Police were deployed at the capital's main intersections and outside government buildings.They fired tear gas at three rallies in which dozens of demonstrators took part in western Cairo, police officials said.In the north of the capital, tear gas was also used against pro-Morsi supporters hurling large firecrackers, they said. The Rabaa al-Adawiya killings of August 14, 2013, when police shot dead at least 700 Morsi supporters as they dispersed a protest camp, has remained a rallying point for Egypt's harried Islamist opposition.Two years on, no policemen have faced trial over the incident.About 10 police were killed during the dispersal, after coming under fire from several gunmen in the sprawling camp on a crossroads in eastern Cairo when they moved to break it up.But rights groups have said police used disproportionate force, killing many unarmed protesters in what Human Rights Watch said "probably amounted to crimes against humanity." The New York-based group called on Friday on the United Nations Human Rights Council to launch an inquiry into the killings.Worst single-day killing"Washington and Europe have gone back to business with a government that celebrates rather than investigates what may have been the worst single-day killing of protesters in modern history," deputy Middle East director Joe Stork said."The UN Human Rights Council, which has not yet addressed Egypt's dangerous and deteriorating human rights situation, is one of the few remaining routes to accountability for this brutal massacre."In Egypt, however, the government has always defended the dispersal, insisting that the Islamists were armed "terrorists".Morsi, the country's first democratically elected leader, ruled for only a year before mass protests prompted the military to overthrow and detain him. He has since been sentenced to death.President Abdel Fattah al-Sisi, the former leader of the army, had pledged to eradicate Morsi's Muslim Brotherhood.The group has been blacklisted and most of its leaders arrested, severely restricting its ability to mobilise supporters to take part in protests.