Sri Lankan soldiers attacked the final patch of Tamil Tiger-held territory from a new direction in their latest attempt to overrun the rebels, the defence ministry said on Tuesday.
The Tigers have been pushed backed into a coastal strip of land measuring just five square kilometres (two square miles), where they are thought to be holding up to 50,000 civilians hostage.
"Troops commenced advancing northwards from the initial forward defences at Wadduvakal," the ministry said, adding that the guerrillas were putting up stiff resistance.
Recent military attacks into the territory have been from the north.
The ministry said troops were progressing with "utmost restraint" to prevent civilians deaths.
"Terrorists have suffered heavy beating from the security forces and are now left in total disarray," the ministry said. It gave no details of casualties in the latest fighting.
The Sri Lankan government has been saying for months that it is about to completely crush the separatist fighters and "free" the trapped civilians.
The United Nations, which says thousands of non-combatants have been killed in fighting this year, has led international calls for the Sri Lankan government to agree to a ceasefire to prevent further bloodshed.