The Liberation Tigers of Tamil Eelam (LTTE) raided an army camp in northwestern Mannar district on Tuesday night, the ministry said in a statement.
The military retaliated, but it was not clear if the guerrillas suffered any casualties.
In the northeastern district of Trincomalee, the Tigers carried out a bomb attack against a rival Tamil group, killing one man and wounding another, also on Tuesday night, the ministry said.
The violence came amid fears of renewed heavy fighting in the east between security forces and the main LTTE group.
Sri Lanka's army chief, Sarath Fonseka, said last week that troops would move to clear the eastern province of LTTE rebels.
The United Nations and international truce monitors have voiced grave concern for 35,000 "desperate civilians" caught in the crossfire between troops and the rebels at Vakarai.
Some 16,000 people have fled the eastern area.
The LTTE is fighting for independence for the island's minority 2.
5 million Tamil community. The