An explosion at a government building on Monday killed 22 people, most of whom were waiting to see a regional official. Police said the bomb was set off by a Tamil rebel.
At least 50 people were reported injured. A stream of cars and ambulances evacuated victims from the area.
The suspected bomber, a man in his mid-20s, was killed, police said. His alleged accomplice, N. Easwaran, was arrested and was recovering from injuries at a hospital.
The explosion came four days after President Chandrika Kumaratunga proposed giving greater autonomy to regions in the north and east where the Tamils have been seeking a homeland for 12 years. But under the plan, the rebels would have to contest elections if they wanted to govern the area, much of which they already control.