Seven persons, including four women, were killed when their car collided with a Kerala State Transport Corporation bus at Nilamel in the district on Friday morning.
The victims belonged to Bharathannur in Thiruvananthapuram district.
Twelve people, most of them passengers of the bus, were injured in the mishap and admitted to hospital.
The bodies of the victims were extricated from the mangled car by police and local people.
The deceased included the driver of the car, police said.