An explosion on a bus killed at least 16 people and injured 30 others in central China, a Chinese news agency reported. But a Hong Kong-based dissident group put the death toll at 30 and said it believed, based on the damage, that the explosion was caused by a bomb. The China News Service, monitored in Hong Kong, said the explosion occurred when the bus was approaching a bridge in the city of Wuhan in Hubei province. The Hong Kong-based Information Center of Human Rights and Democratic Movement in China quoted an unidentified source who went to the scene as saying the bus was gutted by fire after the explosion. Authorities accused Islamic separatists of planting bombs that exploded nearly simultaneously on three buses in the western city of Urumqi almost a year ago and of blowing up a bus in Beijing not long after that.