The move came amid growing international concern over the plight of civilians trapped in the 5km strip of land controlled by the LTTE.
The Sri Lankan government has rejected a call for a truce from the LTTE, demanding the rebels surrender or face defeat.
Tens of thousands of people have fled the area but the UN has said that up to 50,000 civilians could still be trapped.
Yasushi Akashi, an envoy sent by Japan, Sri Lanka's main foreign donor, ended a three-day visit to the country on Saturday.
Akashi called for civilians in the war zone to be protected and for the government to give greater assistance to those refugees from the region who are living in state-run camps in the northeast.
Many of the refugees fled the area while badly wounded or ill.
The military on Saturday denied claims by a government doctor and claims on a Tamil website that they had shelled a makeshift hospital in the conflict zone, killing 67 civilians.
Dr Thurairajah Varatharajah, who works at the hospital, said that the location was shelled twice, injuring 87 other people.
The military has repeatedly rubbished claims that they use heavy weaponry in the conflict zone and blames the LTTE for the attack.
The LTTE have been fighting a war for a homeland for Sri Lanka's ethnic Tamils since 1983.