At least 30 people are dead and another 200 are missing after a boat sank on a lake in the Democratic Republic of Congo, authorities say.

Simon Mboo Wemba, the mayor of Inongo, told reporters on Sunday night that many of those on board the boat that sank on Lake Mai-Ndombe were teachers.

The mayor said they had travelled to collect their salaries by boat because roads in the region are so poor.

It was not immediately known how many people were on board the boat when it hit bad weather late on Saturday.

But officials estimate several hundred were on board. More than 80 people survived.

Boats in the vast nation of DR Congo are usually overloaded with passengers and cargo, and official manifests do not include all those aboard.