The couple - Chandra Jain (67) and his wife Anita (60) - were returning from a temple when the truck hit them from behind near a bus stand, police said.
The two were flung several metres after the truck hit the scooter and their heads crashed on a pavement.
Locals stopped the truck and called up police.
Both riders were not wearing helmets, police said.
The driver was arrested and the couple was rushed to a hospital, where doctors declared them dead, police said.