Two others were wounded in Wednesday night's attack by the Liberation Tigers of Tamil Eelam (LTTE), the ministry said.
There were also sporadic mortar bomb attacks as well as one grenade attack that wounded a constable, it said.
The violence was the latest in an upsurge in bloodshed since December that has left more than 1,500 people dead by official count.
The three-decade conflict has claimed more than 60,000 lives.
There was no immediate word from the Tigers about the latest attack but in talks Wednesday with peace-broker Norway, they accused the government of placing minority Tamils at risk from shelling and air raids.
"He warned that the (majority) Sinhalese population will have to face the consequences soon," the LTTE said in a statement after the head of its political wing, S.
P. Thamilselvan, met with Oslo's envoy Hans Brattskar.
The LTTE also said the rebels told the Norwegian envoy they viewed the military's capture on Monday of the former Tiger-held town of Sampur in t