Sunday's suicide bombing indicates that small groups of separatists were still operating in Eastern province despite last year's government declaration that they had cleared the entire province of them.
In other violence, battles on Saturday in Jaffna, Mannar and Vavuniya districts left 39 separatists and a soldier dead, a military official said on condition of anonymity.
On Sunday, air force jets bombed a camp occupied by separatist commanders in Mannar district, the military said in a statement. It did not give details of casualties or damage caused by the raid.
It was not possible to obtain independent accounts of the battles because reporters are barred from the war zone.
Often the two sides exaggerate each other's casualty figures while underplaying their own losses.
The pro-rebel TamilNet website reported that separatists killed three soldiers across the defence line in Vavuniya district.
The report did not comment on the government's claim that 39 Tigers were killed.
Fighting between the military and the LTTE has escalated since the government formally pulled out of a six-year-old ceasefire pact last month.
Mahinda Rajapaksa, the president, argues that the LTTE used the truce to rearm themselves and were not sincere about peace negotiations.
The LTTE has been fighting since 1983 to create an independent homeland for Sri Lanka's minority ethnic Tamils, claiming decades of marginalisation by the Sinhalese government.
More than 70,000 people have been killed in the conflict.