The United Nations says, attacks on relief workers battling the cholera epidemic in Haiti are seriously hampering the international response to the problem. It is appealing for an immediate end to the violence. Violent demonstrations broke out after local Haitians started blaming foreign UN peacekeepers for introducing the cholera virus to the country.For a second day, protesters paralysed the city of Cap Haitien erecting barricades and throwing rocks and bottles at UN vehicles. The United Nations said it was forced to cancel flights carrying medical supplies and personnel to the north. It said protesters had looted and burnt a world food programme warehouse. The urgent appeal came as the government announced that more than one thousand people have now died of cholera. There are also signs the disease is spreading beyond Haiti's borders with the neighbouring Dominican Republic reporting its first confirmed case.