Joachim Taila, Governor of the Sud-Ubangi Province, said rebels from neighbouring Congo-Brazzaville had attacked the Congolese town of Dongo, located near the border.
Crowds of people then tried to cross the Ubangi River in wooden boats, several of which capsized.
So far, 47 bodies have been recovered from the river, Taila said. A rescue operation is still under way.
Congo is dogged by myriad conflicts, with numerous rebel groups active in the region. (dpa/NAN)