Fierce fighting between government troops and separatist Tamil Tigers across Sri Lanka's embattled north killed 36 rebels and five soldiers, the military said Thursday.

The latest violence occurred Wednesday along the front lines separating government-controlled territory and the rebels' de facto state in the north, said military spokesman Brig. Udaya Nanayakkara.

Army troops and the air force launched a joint offensive on rebel bunkers in Kilinochchi district, triggering a furious battle that killed 18 rebels and four soldiers, he said. The same fighting wounded 31 soldiers. Scattered battles in Vavuniya killed 12 rebels and one soldier, while in Welioya region six rebels died, said Nanayakkara.

Fighting has escalated in recent months on this war-torn Indian Ocean island, with the military capturing a series of rebel bases and large chunks of territory, and officials reiterating a pledge to crush the guerrillas by the end of the year.

Rebel spokesman Rasiah Ilanthirayan could not be reached for comment Thursday.

Both sides routinely exaggerate enemy casualties and underreport their own. Independent verification of the fighting is not possible because most journalists are barred from the war zone.

The latest infantry clashes came a day after Tamil Tigers launched a brazen airstrike on a major naval base in the island's embattled east, wounding 10 sailors. International aid groups say fighting has forced tens of thousands of Sri Lankan civilians to flee their homes.

The rebels have fought for an independent state in the north and east since 1983, following decades of marginalization of ethnic Tamils by governments dominated by the Sinhalese majority.

More than 70,000 people have been killed in the conflict.