The accident happened at night, but it is not clear if it occurred on July 26, 27, 28 or 29 evening.

The ferry was carrying at least 200 passengers on the Tshuapa River.

Boats and ferries are commonly used in DR Congo, which has few viable roads or railways but major lakes and rivers.

However, the vessels are often overloaded or badly maintained, and accidents are commonplace.

A Red Cross representative in the provincial capital Mbandaka said he had received reports that 80 dead bodies had been found in Ingende, the town on the Tshuapa where the accident happened.

It is not known how many people were on board the ferry, Rebecca Ebale Nguma, a provincial spokeswoman, said.

About 100 people had made it to safety but some passengers were still believed to be missing, she said.

Government spokesman Lambert Mende said that the wooden cargo ship was not allowed to sail at night.

An investigation was under way to find out whether port officials in the town of Bumba had authorised its departure, he said.

DR Congo - a country the size of western Europe - has only a few hundred kilometres of tarmac roads outside the main cities.

In April and May, around 200 people died in two successive shipwrecks, leading to the dismissal of the transport minister and promises by the government to enforce better safety standards.