The UN World Food Programme (WFP) has warned that it is running out of money to feed tens of thousands of displaced people in eastern Sri Lanka.
The WFP has warned of an impending food crisis
The WFP estimates that around 155,000 civilians are now displaced in the restive eastern district of Batticaloa.
It has said that around 95,000 people have become displaced in Batticaloa in the past week alone, which has added to the burden of feeding everyone.
Meanwhile four Tamil Tiger boats have been sunk in the north, officials say.
"The problem is that the stocks are dwindling and we will run out of food supplies by the end of April," WFP spokesman Simon Pluess said, adding that the WFP had already suspended several programmes because of a shortage of funds.
The UN has appealed to both sides to provide better access
Correspondents say that camps in Batticaloa district are cramped and overflowing, while sanitation is poor and food increasingly scarce.
Aid agencies in the region are now warning of a major humanitarian emergency.
The WFP says that it is supplying food aid to about 60,000 people living in camps in Batticaloa district through a Sri Lankan government ministry, as well as to another 300,000 people in other districts.
The UN has called on the government and Tamil Tiger rebels to allow "unimpeded access" to the displaced people.
It and other aid agencies have frequently complained of restricted access to conflict areas.
The UN says that sanitation is poor in many camps
The government says that is resettling thousands of displaced civilians in a recently captured rebel stronghold at Vakarai, 225km (140 miles) northeast of Colombo.
But many displaced people say they are reluctant to be resettled, pointing out that the authorities are already struggling to cope with an influx from rebel-held areas.
Meanwhile the army says that its artillery fire destroyed four rebel boats off the country's northern coast.
It said that navy ships and troops manning artillery positions along the coast have been ordered to look out for rebel shipments of arms and ammunition.
"Four Tiger boats were sailing toward the coast when they were observed by our troops. These four rebel boats were destroyed," Lt Col Upali Rajapakse told the Associated Press news agency.
There has been no comment on the incident from the rebels.
The Sri Lankan conflict has killed around 68,000 troops, civilians and rebels since 1983, with around 4,000 of those dying in the last 15 months alone.