Government forces say they are steadily advancing on the town of Kilinochchi in an offensive that began over a year ago.
The Tigers, who are known for their trademark suicide attacks, have put up only intermittent resistance to the military forces advancing on several fronts in northern part of Sri Lanka known as the Wanni.
The capture of Kilinochchi would be a major blow to the Tigers, who set up the town as the capital of their mini state after taking the area from government forces 10 years ago.
The rebels have not suffered such a setback since December 1995 when they lost the northern peninsula of Jaffna, which they considered their cultural capital.
Retired army Brigadier General Vipul Boteju said the success of the latest military campaign appeared to be due to the use of small groups along a broad front.
Past attempts to take Kilinochchi using large columns of soldiers had failed because the Tigers deployed suicide bombers against them.
But a defence analyst who decl