The latest deaths raised to 64 the number of people, mostly police or troops, killed in bomb attacks in the past week in the latest surge of violence linked to the decades-old Tamil separatist conflict.
On Sunday night the rebels said they were suspending their participation in talks set to take place in Switzerland next week on saving a shaky Norwegian-arranged truce that has been in place since February 2002.
Five of those killed Monday were soldiers who died when a powerful Claymore landmine exploded near their truck in Vavuniya district, a military official said from the town of Vavuniya, 260 kilometres (160 miles) north of Colombo.
Seven soldiers were wounded in the attack, which the official blamed on Tamil Tiger guerrillas.
"They blocked the truck by driving a three-wheeler (taxi) across the road," he said.
"Within a few seconds the three-wheeler exploded.
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Another Claymore mine exploded further north in the Jaffna peninsula, killing the man who was carrying it and two others,