Hospital authorities say children and women are among the injured
Medical staff in Sri Lanka say at least 18 civilians have been killed as the military continues its offensive on the northern bases of Tamil Tiger rebels.
Hospital officials said the number killed in fighting around Kilinochchi and Mullaitivu could be much higher.
The military said Mullaitivu - the last major rebel stronghold - was now surrounded, but it denied rebel claims that civilians came under attack.
A military spokesman told the BBC that the allegation was propaganda.
Aid agencies say they are concerned about the fate of the 250,000 civilians living in rebel-held territory in the north of the country.
According to a Tamil Tiger statement and reports on the pro-rebel TamilNet website, the Sri Lankan military attacked civilians in rebel-held villages around Kilinochchi and Mullaitivu.
But army spokesman Brig Udaya Nanayakkara dismissed the claims that 18 people had been killed and more than 40 injured in the strikes.
He told the BBC's Sinhala service that the Tamil Tigers' claim was propaganda "as they have been cornered and are seeking international attention".
The Sri Lanka army says it is closing in on the rebels
Earlier, an army spokesman said rebel resistance was crumbling fast.
The Tigers have lost a considerable amount of territory to government forces in the last few months, including key strongholds Kilinochchi and Elephant Pass.
The two sides have differed widely in their reports of casualties.
Independent journalists are prevented by the government from travelling to the conflict zone, so it is impossible to verify the casualty claims made by both sides.
The Jaffna peninsula and its capital have been regarded as the heart of the 25-year-old separatist insurgency.
The Tigers are fighting for a separate homeland. At least 70,000 people have been killed in the fighting.