They were found unconscious in a hotel in Daman of Makwanpur district Tuesday morning.
Nepal Police spokesperson Shailesh Thapa Kshetri told our Kathmandu correspondent that 15 Indian tourists have checked into a resort in Daman last night.
They had booked four rooms but eight of them stayed in one room and turned on a gas heater to keep warm. Mr. Kshetri said all eight people were found unconscious in the morning and airlifted to Kathmandu for treatment.
They were declared dead at the hospital. The deceased include two couples and four children. All of them were from Kerala.
The bodies of deceased will be handed to their relatives after postmortem.