Government soldiers consolidating their new positions in Kilinochchi, the former Tamil political base, cleared mines and booby-traps from abandoned buildings, an AFP photographer flown to the area reported.
Gunfire and intermittent artillery barrages erupted around Kilinochchi, which was captured by security forces on Friday after nearly two years of fighting.
Troops clashed with the Liberation Tigers of Tamil Eelam (LTTE) on Saturday at four locations outside the town, the ministry said.
"Both sides suffered casualties," a military official said, without giving further details.
The defence ministry said ground forces, backed by helicopter gunships and planes, were moving towards Mullaittivu, the jungle district along the northeastern seaboard, where the Tigers have their main military facilities.
Military officials said troops were also heading further north of their positions in Kilinochchi to retake the strategically vital Elephant Pass which was lost to the Tigers in