In the first incident, seven people died and seven others sustained injuries in western Gulmi district when a micro-bus heading towards Tamghas in Gulmi skidded off the road and rolled down a hill, the police said.
The injured were admitted to Shringa Health Post, Palpa for medical treatment.
In the second incident, four people were killed while six others were injured when a jeep en route to Jayaramghat from Katari Bazaar fell 400 meters in Katari Municipality along the Siddhicharan Lokmarga.
The accident took place after the driver lost control of the jeep at 1:30 pm, said police.
On Saturday, an overcrowded passenger bus veered off a road and plunged into a river in central Nepal's Dhading district, killing 31 people, including an Indian woman.