The Sri Lankan military says at least 15 civilians were killed and 25 wounded when a roadside bomb exploded near a crowded passenger bus in the north-central part of the country.
The government has blamed Tamil Tiger rebels for the explosion. No other details are immediately available.
Earlier in the day, the Sri Lankan military said its troops had killed 29 Tamil rebels in battles in the north. It said seven soldiers also were killed in the fighting, which began Tuesday in the districts of Mannar and Vavuniya and continued Wednesday.
In another development, international and local human rights groups are condemning the Sri Lankan government for the recent mass arrests of minority Tamils.
More than 2,500 Tamil civilians were arrested last week during a security crackdown after two bomb attacks in Colombo killed 20 people.
Tamil rebels were blamed for the bombings.
Some information for this report was provided by AFP, AP and Reuters.