The China Eastern Airlines aircraft took off from Kunming and was flying to Guangzhou when it crashed to the ground in a mountainous area near the city of Wuzhou, sparking a strong fire in nearby forest.
Flight MU5735 had 123 passengers and nine crew members on board, the Civil Aviation Administration of China said on its website.
The fire has been extinguished and rescue operations are under way, said Chen Jie, an official with the regional emergency management department.
China Eastern Airlines promised to thoroughly investigate the cause of the incident and set up nine special working groups for handling the aircraft wreckage, accident investigation, support for the families of the victims, legal assistance, among others.
President Xi Jinping ordered all search and rescue efforts.
The president also asked to take all measures to identify the cause of the accident and strengthen the safety review of the civil aviation sector, in order to guarantee the absolute safety and life of the population.