Riot police battled protesters outside Greece's parliament and in Athens suburbs on Tuesday while opposition socialists called for the conservative government to quit to end the worst civil unrest in decades. Rows of riot police squared off with demonstrators for more than an hour outside the parliament building before firing teargas to disperse the crowd in fresh violence triggered by the shooting of a 15-year-old boy by police. Bands of young protesters regrouped and threw stones at police, chanting: "Let parliament burn" On the fourth day of violence, protests spread to the Athens suburbs after the funeral of the boy, Alexandros Grigoropoulos, whose killing on Saturday triggered Greece's worst riots in decades, fanned by discontent over government and a slowing economy. More than 5,000 people clad in black gathered at the cemetery, many chanting: "Cops, Pigs, Murderers." As the boy's flower-covered white coffin was being buried, protesters clashed with police outside and one officer fired shots in the air to disperse an angry crowd. His killing touched a raw nerve among young Greeks, outraged at years of political scandals and rising levels of poverty and unemployment, worsened by the global economic downturn. Prime Minister Costas Karamanlis, whose New Democracy party has a one-seat majority, held emergency talks with the president and opposition leaders to urge them to close ranks against the rioters. "We must all have a united stand against illegal actions, to clearly condemn violence, looting and vandalism," he said, and appealed to unions to cancel a protest rally during a 24-hour strike scheduled for Wednesday. Police fear the strike, expected to ground flights and bring Greece, a member of NATO and the European Union, to a standstill, will fuel more violence. Both requests were quickly rejected by leftist union leaders and politicians who say the government's reforms have worsened conditions for the one-fifth of Greeks below the poverty line. "The government has lost people's trust," said the leader of the socialist opposition party, George Papandreou. "The only thing this government can offer is to resign and turn to the people for its verdict."