Sri Lankan troops launched a major attack Monday against Tamil rebel fortifications, sparking clashes that killed 57 insurgents and 10 soldiers, the military said.

Government forces have seized a large area of rebel-held territory in recent months and backed the rebels into small areas in the lush jungles of the island nation's northeast.

However, troops have been locked in heavy battles at the edge of Kilinochchi, the rebel administrative capital, for nearly two months amid heavy rains and stiff fighting. The government claimed last month the fall of Kilinochchi was "imminent."

The army killed 57 insurgents and lost 10 soldiers in a bid to capture an earth berm fortification erected by the rebels to protect their de facto capital, military spokesman Brig. Udaya Nanayakkara said.

The military succeeded in seizing another mile-wide stretch of the 11-mile long earthen bunker Monday. The army now controls more than 4 miles, Nanayakkara said.

With most communication cut to rebel areas, Tiger spokesmen could not be reached for comment. Independent verification was also not available because journalists are barred from the war zone.

The battle was the latest in weeks of fierce ground fighting in the region, with the rebels saying Sunday they killed 60 government troops the day before. The military denied the claim, saying it lost 12 soldiers in the fighting.

The Tamil Tigers have been fighting since 1983 to create an independent homeland for ethnic minority Tamils, who have suffered decades of marginalization by successive governments controlled by the Sinhalese majority.

The conflict has killed more than 70,000 people.