Tens of thousands of Liberians who have registered as refugees in neighbouring Guinea are crossing the border to trade their food rations and prepare their eventual return before returning to their camps for the next handout, aid workers said. Aid workers admit that this unofficial flow of food across the border is probably helping to keep thousands of needy people fed in outlying districts of war-ravaged Liberia, where rebel gunmen still control the border. Recent attempts to clamp down on wandering Liberian refugees by counting the population that is actually resident in four official refugee camps in Guinea's southeastern Forest Region have sparked violence.