The bus, heading from southern Johor state to the capital Kuala Lumpur, went off the road in the wet before rolling over and ending up in a deep ditch, said Mohammad Yusof Mohammad Gunnos, deputy director of the fire and rescue department.
The incident happened in the early hours in Johor state. Details of those killed were not immediately known, he said, adding that the injured were being treated in the Muar district public hospital.
"This pre-Christmas tragedy is so far the most horrific accident in Johor state for 2016," he told AFP. Deadly road accidents are common in Malaysia despite efforts to crack down on poor driving, especially during festive seasons when people return to their home towns.