Tamilnet.com said two shells fired by government forces hit the makeshift hospital at Mulliavaikal in the Mullaittivu district three days after its location was given to the military through the International Committee of the Red Cross.
There was no immediate comment from the ICRC which has limited access to the combat zone, but the military denied targeting the area.
"We have not carried out any shelling, but we heard some loud explosions inside the no-fire zone and it could have been a misfire by the Tigers," a military spokesman, Udaya Nanayakkara, said.
Charges and counter claims by both sides cannot be verified as there are no independent observers in the conflict area and the government has rejected international calls to allow neutral humanitarian access.
The latest reports of civilians casualties came as Japan’s special envoy to Sri Lanka Yasushi Akashi held talks with President Mahinda Rajapakse on the humanitarian crisis.
A presidential spokesman said Akashi was told that the government wanted the Tigers to surrender and allow some 20,000 civilians still trapped in a small sliver of beach to leave to safety.
Sri Lanka’s defence ministry on Saturday rejected satellite imagery issued by the United Nations in support of allegations that security forces shelled a civilian area last month.
The defence ministry said the allegations, based on UN aerial images posted on the UNOSAT website and used on several foreign television channels, had "no scientific validity" unless there was verification on the ground.
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