BANGKOK - Twenty-one people were killed, 18 others injured on Thursday as a bus plunged into a ravine in northern Thailand, local media reported.

The bus, rented by a group of residents from Chiang Mai's Saraphi district who were returning home after making merit at a temple in the neighboring Lampang province, veered off a steep downhill road, rammed through the guardrail and fell into a 30- meter-deep ravine.

Twenty-one passengers were killed on the scene and 18 others, including the driver, were seriously wounded and rushed to a nearby hospital.

An online report by the Thai News Agency put the death toll at 23.

Police said the driver was unfamiliar with the route and the bus had a brake problem.