Authorities in Madagascar said on Wednesday that the death toll from a plague outbreak has reached 124 people as the disease for the first time affects the island's two biggest cities.

The nation's disaster risk management office says 1,192 cases have been identified. More than two-thirds of cases are of the more virulent pneumonic form.

The office says less than 30 per cent of people who have had contact with plague patients can be traced, making it more difficult to control the spread of the disease.

Plague is endemic in Madagascar. This year's outbreak is unusual because it has reached the nation's two largest cities, Antananarivo and Toamasina.