At least 20 people have been confirmed dead following an outbreak of cholera in the northern gas-rich province of Cabo Delgado, the state-linked Noticias newspaper reports.
The health authorities are reported to have declared an outbreak in three districts of Cabo Delgado: Macomia, Mocimboa da Praia and Ibo.
The provincial director of health, Anastacia Lidimba, said the outbreak began on islands off the Cabo Delgado coast, where people had taken refuge in unsanitary conditions to flee from attacks by Islamist insurgents on the mainland.
She said the situation was bad on Matemo and Congo islands.
Dr Lidimba said so far 273 cases of the water-borne disease had been diagnosed.
Teams of doctors and medicine have been sent to the affected areas.