In Feni, a woman and her daughter were killed and three people injured as a speedy bus hit their auto-rickshaw at Tebaria village in Sadar upazila.
The deceased were identified as Johora Begum, 36, and her daughter Faria Akhter, 16, of the village.
The bus hit the CNG-run auto-rickshaw on Dhaka-Chattogram highway around 8pm, leaving five people injured, said chairman Mosharraf Uddin of Lemua Union Parishad.
Locals took them to Chittagong Medical College Hospital where doctors declared Johora and Faria dead, he said.
In Laxmipur, two members of a family were killed in a head-on collision between a human hauler and a motorcycle at Gugibari in Ramganj upazila.
The deceased were identified as Md Sumon Hossain and his nephew Md Tamim Hossain, residents of the upazila.
The human hauler collided with the motorcycle around 8pm, killing Tamim on the spot, said Md Anwar Hossain, officer-in-charge of Ramganj Police Station.
Sumom was taken to upazila health complex where doctors pronounced him dead, the OC added.