Aid officials, including UN agencies have reported that about 134,000 people were displaced from their homes in Wanni as a result of the current wave of fighting.
Tens of thousands of people have died on both sides since the Liberation Tigers of Tamil Eelam launched a separatist campaign in 1972 for a homeland for minority Tamils in the island's north and east.
The few aid agencies, including UN organisations, still operating inside rebel-held Wanni in northern Sri Lanka were told they should quit the area immediately, disaster management minister Mahinda Samarasinghe said.
"We have told them that we are not in a position to guarantee their safety given the present situation," Samarasinghe said.
"We asked to leave the Wanni immediately with all their resources. They wanted a week or two to comply.
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He said defence secretary Gotabhaya Rajapakse explained to representatives of aid agencies Monday that Tiger rebels could attack humanitarian workers to shift the blame onto government forces