Sri Lanka hit back earlier this week against human rights and aid groups, accusing them of supporting the rebels and of trying to prolong the island's civil war.
Speaking here after he was given special government permission to visit Vavuniya in northern Sri Lankan earlier this week, aid official Esko Kentrschynskyj said: "We want to reassure the Sri Lankan government we are not against them.
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"We are just asking to be partners," added Kentrschynskyj, head of the European Commission's Humanitarian Aid department (ECHO) unit for Asia and Latin America.
"We see our role as complementary to the government in meeting the humanitarian challenge," which could quickly spiral out of control, he said.
Kentrschynskyj, who visited relief centres in Vavuniya, said refugees from the fighting between government troops and Tamil rebels were streaming into camps at a rate of 1,000 a day.
The International Committee of the Red Cross is currently the only international humanitarian organ