The London-based rights group said the Colombo government lacked the capacity to provide basic essentials and safety for those who have had to flee escalating fighting with Tamil Tiger rebels.
Amnesty called on the government to allow independent international monitors into the northern Wanni region to oversee and ensure that convoys with food, medical and other essential supplies enter and are distributed.
The United Nations announced it was pulling all its staff from the Tamil Tiger-held north this week after the government gave them two weeks to quit the area ahead of a major military showdown.
Local workers from international aid agencies left behind in the region fear that the withdrawal of international staff will make them more vulnerable to abuses by the Liberation Tigers of Tamil Eelam (LTTE), Amnesty said.
"Aid agencies provided a lifeline to tens of thousands of trapped civilians," said Sam Zarifi, Amnesty International's Asia Pacific Director.
"If aid workers are