There has been no reaction from the guerrillas, who have launched scores of similar suicide bombings in the past.
Tuesday's bombing in the south of the island was an act of "desperation" by the Liberation Tigers of Tamil Eelam (LTTE) who have been cornered in jungle terrain by security forces, a government statement said.
"This is another desperate act that the LTTE terrorists, now on their last legs, have perpetrated to divert attention," it said.
"The government remains unwaveringly committed to rid the country of the terrorist menace and bring about peace. This attack will only serve to strengthen the resolve of the government and the security forces."