There have been continued heavy clashes between Tamil Tiger rebels and Sri Lankan forces in the island's north.
International monitors said they could not verify the numbers killed
It follows a day of intense bloodshed in which seven people died in a bombing in the capital, Colombo, and government air strikes killed at least 19 people.
The government has closed all schools for two weeks, in case of reprisal attacks following the deaths of Tamils.
The Tigers say 61 girls were killed in an air raid that struck an orphanage, but the government denies it.
The government says its jets hit a rebel training camp in the rebel-controlled northern district of Mullaitivu.
International truce monitors and UN staff said they had found no evidence the site was used as a military base.
However, they were unable to verify the number of people killed.
They reported seeing the bodies of 19 people at a nearby hospital, most of them women around the age of 18.
The government says rebels have infiltrated civilian areas in government-controlled territory and a massive search operation is under way.
The Jaffna peninsula has become the centre of Sri Lanka's conflict.
The Tamil Tigers and army have exchanged artillery strikes along their de facto border.
Monday's bomb in the capital, Colombo, targeted the Pakistani High Commissioner's convoy, killing seven people.
Bashir Wali Mohamed, who was uninjured, said he believed he had been targeted because of the Pakistani government's support of the Sri Lankan government in its war against terrorism.
The Tamil Tigers' military spokesman, Irasaiah Ilanthirayan, told the BBC they were not responsible for the blast.
The incident has raised fears the international community is being drawn into the violence.
Pakistan has condemned the attack on its ambassador
The first one-day international of the triangular series with South Africa and India has been postponed because of concerns over security, officials said.
Sri Lanka were scheduled to play the South Africans on Monday but the game was rescheduled for Tuesday due to wet weather.
The Tigers have ruled out peace talks with the government while heavy fighting continues between the two sides.
Aid agencies say about 100,000 people have been affected by the latest fighting.
The recent flare-up in fighting has alarmed Sri Lanka's key foreign donors - the US, Japan, the European Union and Norway - who have called for an immediate end to the hostilities, which they said were "seriously unravelling" the 2002 ceasefire agreement.
The ceasefire aimed to halt more than two decades of war between the government and the rebels, who are fighting for an independent homeland for the country's minority Tamil people in the north and east.
It remains officially in effect, despite months of violence.