Malawians have expressed concern after the water in Lake Malawi turned green in a rare phenomenon.

The fisheries department has warned fishermen against fishing on the lake saying it could be harmful.

Forestry and Natural Resources Minister Nancy Tembo has explained that the greening is as a result of a bloom in toxic algae that occurred after heavy rains and wind mixed up the nutrients found at the bottom of the lake.

Ms Tembo said the lake had become eutrophic - a condition where aquatic life begin to die off as oxygen levels reduce - and warned people to stay away and give the green water two weeks to fade away.