Brigadier Prasad Samarasinghe, a military spokesman, said suspected Tamil Tiger rebels set off an anti-personnel mine in the northeastern district of Trincomalee on Friday, killing a village guard and wounding another policeman.
He said the men had been checking a road used by military vehicles when the mine exploded.
Also on Friday, a civilian, believed to be a Tamil, was killed when villagers attacked Tamil homes, a police officer in the area said.
The killings come just days before a scheduled meeting between rebels and government representatives.
The groups were set to meet in Geneva on April 24 - 25, but on Thursday, S P Thamilselvan, the leader of the Tamil Tigers' political wing, said that they would boycott the talks because of escalating attacks on Tamils.
Norway, which brokered a now battered ceasefire agreement in 2002, has been pushing hard for both sides to return to negotiations.
Erik Ivo Nurnberg, a spokesman for the Norwegian Embassy, said: "We are in touch with both the parties to make them meet."
Facilitating peace talks
Ulf Henricsson, the head of a Nordic ceasefire monitoring mission, headed to Kilinochchi on Friday to try and resolve a dispute over transporting rebel commanders to their headquarters for an internal meeting.
The rebels insist on having the internal meeting before holding any talks with the government.
Helen Olafsdottir, a spokeswoman for the Sri Lanka Monitoring Mission, said truce monitors were trying to facilitate transport to enable peace talks soon.
More than 55 people have been
killed in Sri Lanka since early April
Nurnberg declined to say if Norway's latest efforts were aimed at persuading the rebels to attend the scheduled Geneva talks, or to set new dates for the meeting.
The Geneva talks were meant to salvage a ceasefire that is faltering due to escalating violence in Sri Lanka, where more than 55 people - 33 of them government soldiers - have been killed since early April.
The Tigers have fought the government since 1983, demanding a separate Tamil homeland and accusing the Sinhalese-dominated government of discrimination.
More than 65,000 people were killed in the fighting before the ceasefire.