Sri Lanka's military says a bomb has exploded near the capital, Colombo, wounding a bus driver.
Military officials say the bomb - believed to be a mine - went off near navy personnel, the apparent target of the blast.
No one has claimed responsibility, but similar attacks have been blamed on Tamil Tiger rebels.
The incident happened as government officials and Tamil rebels are preparing to open talks in Oslo on Thursday to review a Norwegian-brokered ceasefire.
There has been a recent upsurge in clashes between Tamil rebels and Sri Lankan government forces. Hundreds of people have died in recent months. Observers fear the clashes could wreck the existing ceasefire and re-ignite a civil war.
Tamil rebels have been fighting for more than two decades for a separate homeland in Sri Lanka for the nation's ethnic minority Tamils. Tens of thousands of people have died in the conflict.
Some information for this report was provided by AFP and AP.