An accident in south Ecuador involving a passenger bus left at least 16 people dead and eight others injured, rescue officials have said.

"So far the toll is 16 dead and eight injured" from the crash, which involved another vehicle and took place in Ecuador's Loja province bordering Peru, the ECU911 agency said on WhatsApp.

"Firefighters, the National Police and the Ministry of Public Health units are working on the incident, which involved an interprovincial transport bus and a light car-type vehicle," the agency said.

The bus had collided with a car travelling in the opposite direction and overturned dramatically, according to local media.

Traffic accidents are among the main causes of death in Ecuador.