PORT-AU-PRINCE, July 14 (Reuters) - Scattered protests broke out in Haiti"s capital on Wednesday as gasoline shortages added to concerns over insecurity and access to basic goods a week after the assassination of President Jovenel Moise pitched the Caribbean nation into uncertainty. Nearly all the gas stations in Port-au-Prince were closed and long lines formed outside the few that were still operating, with residents blaming both the criminal gangs that control key supply routes as well as opportunistic black market fuel sellers paralyzing distribution into Haiti"s biggest city. Some protesters set tires ablaze in the middle of gritty city streets, which remain quieter than usual in the aftermath of Moise"s killing early last Wednesday. Moise was shot dead at his home by what Haitian authorities describe as a unit of assassins, including 26 Colombians and two Haitian Americans. A third Haitian American, Christian Emmanuel Sanon, was arrested on Sunday by Haitian authorities, who accused him of being a mastermind of the attack. Prosecutors have been preparing to question the head of Moise"s security team, Dimitri Herard. It is not clear if the questioning has yet taken place. The killing came amid a surge in gang violence in recent months that has displaced thousands and hampered economic activity in what is already the poorest country in the Americas. At the justice ministry where Herard is to be questioned, graffiti spray-painted on the wall declared, "We reject the power of the gangs." Eugene France, 63, said he was struggling to sell any of the men"s dress shoes he had slung around his neck and feared more violence. "No one is safe, not even the police," he said, speaking outside the ministry. "I"m scared because the gangs just keep killing people and I can"t sell anything." Outside the national palace, a small crowd gathered at a makeshift memorial with flower arrangements, rows of white candles and a Haitian flag at half mast in front of a large photograph of Moise. Damy Makenson, a 30-year-old office worker, slowly approached the memorial, laid down some flowers and solemnly made the sign of the cross over his head and chest. "He died working to remake Haiti, and I want you to know that his ideas did not die with him," he said, comparing Moise to Jean-Jacques Dessalines, a Haitian founding father and military leader who helped put an end to French colonial rule in the early 1800s. In New York, Haiti"s U.N. Ambassador Antonio Rodrigue on Wednesday appealed for international help. "At this uncertain time, Haiti needs the support of the international community more than ever," he told the 193-member U.N. General Assembly, where ambassadors stood to mark a moment"s silence to honor Moise. Rodrigue listed organizing democratic elections and the government"s ability to meet Haiti"s socio-economic needs as challenges facing the nation. The U.S. Ambassador to the United Nations, Linda Thomas-Greenfield, said a U.S. delegation recently in Haiti had called for dialogue to help enable free and fair presidential and parliamentary elections. The United States is still evaluating Haiti"s request for assistance, and its focus is helping the Haitian government "with navigating the investigation into the assassination of President Moise," State Department spokesman Ned Price said. "The Department of Justice will continue to support Haitian authorities in their review of the facts and the circumstances surrounding this attack," Price said at a news briefing on Wednesday.