The incident occurred when the victims were returning from Velankanni in their car after offering prayers at a church there.
The deceased hailed from Kasargod district in Kerala, police said.
Four persons, including a child, who were injured in the accident, have been hospitalised, they said.
Kerala Chief Minister Pinarayi Vijayan, meanwhile, said in Thiruvananthapuram that necessary arrangements have been made to bring the bodies to the state.
He said the state police was in touch with their Tamil Nadu counterparts in this regard.