( CNN ) -- Flash floods have inundated refugee camps in northern Sri Lanka , endangering more than 16,000 Tamil refugees who only months ago survived cross-fire in the country 's two-decade civil war , the United Nations says . In this file photo Tamil civilians are seen at Menik Farm refugee camp on the outskirts of Vavuniya , Sri Lanka . Three days of heavy rains have damaged or destroyed nearly 2,000 shelters housing the refugees in the Vavuniya District and in Menik Farm , according to the U.N. Office for the Coordination of Humanitarian Affairs . An internal U.N. memo obtained by CNN painted a dismal picture for the refugees , who have been caught in mud flows and the runoff from flooded latrines . `` Due to heavy showers on 14 August 09 ... many tents and toilets were submerged/badly damaged , '' the memo said . `` Reportedly more than 300 families gathered together and marched towards the main access gate of the Zone to protest , '' the memo continued . `` Though ... not violent , they seemed disgruntled and agitated due to the sufferings and expressed their resentment by hooting and making noises . '' The camps spread across northern Sri Lanka are home to about 280,000 people , who were displaced in the final months of the nation 's civil war . The flooding came ahead of Sri Lanka 's monsoon season , which typically brings heavy rains to the country 's northeast from October till January . `` If the rain continues , which is very likely , then the overall situation may go out of control of the management and lead to serious security threat , '' the memo warned , saying contingency plans are being `` discussed and worked out . '' Human Rights Watch has called for the immediate release of Tamil civilians living in the camps , which are surrounded by barbed wire , saying they are being confined against their will , like criminals . `` Those are not detention camps , '' Lakshman Hulugalle , a Defense Ministry spokesman , said in late July . `` They are relief villages . All the basic facilities are being given to the people . '' Hulugalle said that barbed wire is commonly used to define barriers in Sri Lanka and that military guards were being used out of security concerns . The government fears that rebels are hiding in the camps and is screening people living in them . Sri Lanka declared victory in May in its 25-year battle with the Tamil Tiger rebels , but concerns remain about how the island nation can heal its deep war wounds . The rebels -- formally known as the Liberation Tigers of Tamil Eelam -- had waged war for an independent state for minority Tamils in Sri Lanka since July 1983 . As many as 70,000 people were killed in the conflict . Last month the government said it had a 18-day plan to resettle most of the refugees , but added that a lot of work remains to be done to infrastructure and basic services destroyed in the fighting . Human rights activists say , however , that the government is not working fast enough . Human Rights Watch said Sri Lanka 's goal now was to resettle only 60 percent of the refugees by year 's end .
Refugees caught in mud flows , runoff from flooded latrines , internal U.N. memo says . More than 300 families protest conditions , memo says . Flooding comes ahead of Sri Lanka 's monsoon season . Human Rights Watch has called for immediate release of Tamil civilians at camps .