THE scattering of hundreds of thousands of refugees throughout Tamil Tiger-controlled northern Sri Lanka is frustrating United Nations and aid workers. Officials involved in distributing aid talked of several worries as trucks loaded with clothes and food left the frontier post of Vavuniya yesterday for the three-hour drive to Kilinochchi, south of the Jaffna peninsula. UN High Commissioner for Refugees (UNHCR) field officer Kilian Kleinschmidt said the huge movement of displaced people in the past few weeks had no current comparison. 'It is not Africa where refugee camps are filled with people all in the one place; people have left Jaffna as the fighting has forced them out, but they are spreading all over the north,' he said. Their numbers are estimated at up to 500,000. Jaffna had a population of more than 800,000 people, more than a quarter of whom lived in the mainly Sinhalese south. Now the Government and aid agencies face the daunting task of feeding and clothing them as well as containing disease. 'Normally, you would have refugee camps where all the food trucks go to, all the medical supplies go to and all the clothes go to,' said Mr Kleinschmidt. 'But here we have people all over northern Sri Lanka who need assistance in varying forms.' The Government has maintained a tight hold over the distribution of aid into the Tamil separatist stronghold of Jaffna town. Vavuniya, 250 kilometres north of Colombo, is the final outpost of the government-controlled area and yesterday armoured vehicles and tanks were sent through the military checkpoint to join the growing buildup of troops hoping to seize the psychologically important town. But some analysts have reservations about the risk of making the final military push into a virtual ghost-town, believed to be laced with mines and booby traps. The military, wise to the tactics of one of the world's most effective guerilla organisations, believe there may yet be about 40,000 rebels and civilians in the town. To take control of Jaffna would erode any power base the Tamil Tigers have left in the north. Meanwhile, Mr Kleinschmidt expected cholera, dysentery and malaria to become key problems as people struggled against fatigue from travelling to safer areas south of the peninsula. Monsoon rains periodically sweep the region at this time of year. However, charities like Medecins Sans Frontieres (MSF) and the Save the Children Fund can only distribute aid supplied by the Government. An MSF official said this had caused problems because MSF used purpose-built equipment and purpose-made supplies for relief situations, which the Government could not provide. 'It is difficult to do what we have to, the equipment and supplies are not what we normally work with,' he said. But in a statement repeated yesterday, the Government said it would continue to administer the distribution of relief supplies to keep them from the Tigers. Two UNHCR trucks left Vavuniya on Wednesday night with badly needed clothing for refugees living in and around Kilinochchi. Most of the people who fled the Jaffna area did so at short notice with only the clothes they were wearing. Trucks loaded with food and clothes left Vavuniya for northern towns yesterday.