It also came on a day Mahinda Rajapaksa, the Sri Lankan president, unveiled his budget for the coming year.
Documents showed defence spending at 166.45 billion rupees ($1.5bn), its highest ever.
Describing Wednesday's battle, the Sri Lankan military said fierce fighting erupted along a heavily defended border that separates government and rebel-held territory on the peninsula.
It said soldiers held territory on the rebel side of the line for two hours.
"The troops went ahead and captured the terrorist line and in the fighting killed 52 terrorists and a large number of other LTTE cadres were injured in this firefight," said a spokesman at the Media Centre for National Security, declining to be named in line with policy.
"Eleven soldiers were killed and 41 were injured in the clashes."
Rasiah Ilanthiraiyan, an LTTE spokesman, said the Tigers foiled a bid to overrun their bunkers on the Jaffna forward defence line.
"I suggest Sri Lanka tries to prepare negotiations to end the long rebellion in order to give peace a chance"
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"The Sri Lankan military came with the support of heavy artillery, multi-barrel rocket launchers, mortars and back-up fire from helicopters and tanks," he said by telephone from rebel-held Kilinochchi.
"It was a wide-range attempt. It's from Kilali to Muhamalai on the A9 highway. The clash lasted about two hours, and they fell back to their original positions with heavy casualties."
Separately, a report on the defence ministry's website said security forces had confronted Tiger fighters in five separate incidents in the past 24 hours.
It said the troops were responding to LTTE attempts to infiltrate forward defence lines in the northern district of Vavuniya and neighbouring northwestern district of Mannar.
The website cited military sources as saying eight Tigers had been either killed or seriously wounded in the clashes.