Sri Lankan security officials say a land-mine explosion on Wednesday has killed two soldiers and a policeman.
Separatist Tamil rebels are being blamed for the blast, which wrecked a military vehicle near Vavuniya a government-held town in northern Sri Lanka.
Norwegian peace mediators are returning to Sri Lanka later this week in an attempt to save the deteriorating peace accord that the rebels and authorities in Colombo signed four years ago.
Almost 300 people have been killed across Sri Lanka in a recent wave of violence since early April that has aroused concern about a return to civil war.
Before the 2002 cease-fire, more than 60 thousand people died during two decades of conflict between the government and Sri Lanka's ethnic-Tamil rebels.