At least 16 people have been killed in an explosion on a bus carrying civilians in Sri Lanka's eastern district of Ampara, officials say.
The bomb went off as the bus stopped at a security checkpoint
The government has accused Tamil Tiger rebels of being behind the blast, but they deny involvement.
The bombing follows a weekend of violence in which six tsunami reconstruction workers were shot dead.
Worsening violence in recent months, mainly in the east and north, has left tens of thousands homeless.
Monday's explosion happened on the main road connecting Ampara and Badulla.
"The bomb went off just at the Kondawattuwan check point," a police officer told AFP news agency.
"We now believe that the blast was aboard the bus. It may have been a parcel bomb or even a suicide attack."
"Three people were dead on admission and 13 others died in hospital," a hospital official said, adding that 25 more people were undergoing treatment.
Three children and 11 women - one of them a soldier - were killed, said Lankathilaka Jayasinghe, the head of Ampara's main hospital.
The defence ministry has put the blame for the bomb attack on the Tigers.
The rebels have, however, denied any involvement.
The six tsunami reconstruction workers, all ethnic Sinhalese, were killed on Sunday in the eastern district of Batticaloa.
They were building an orphanage for survivors of the 2004 Indian Ocean tsunami that devastated much of Sri Lanka's coast.
The government says the Tamil Tigers killed them. The Tigers blame a group that broke away from them, led by Colonel Karuna, which the Tigers say fights alongside the army against the Tigers.
The bodies of two people shot dead by unknown gunmen were found in the northern Vavuniya area on Sunday night, the pro-Tamil Tiger website says.
Both the Tigers and the military are, officially, still observing a 2002 ceasefire which has become meaningless in practice.
Violence began to increase after the 2005 election of President Mahinda Rajapakse. Since then about 4,000 people have been killed.
In one of the worst incidents more than 60 people - many of them children - were killed in a mine attack the government said the Tigers carried out on a bus in the town of Kabithigollewa, 200km (125 miles) north of the capital, Colombo, last June.
In recent weeks the army has made gains into Tamil Tiger territory in the east.
The Tigers are fighting for a Tamil homeland in the north and east of the island.