A bomb tore through a packed bus carrying civilians Saturday in central Sri Lanka, killing 20 people and wounding 50 others, the military said. The blast inside the bus occurred at 7:05 a.m. in Dambulla town, about 150 kilometers (90 miles) northeast of the capital, Colombo, said military spokesman Brig. Udaya Nanayakkara, blaming separatist Tamil Tiger rebels. A spokesmen for the rebels could not immediately be reached for comment. The group, listed as a terrorist organization by the U.S. and European Union, routinely denies responsibility for such attacks.