A security source said the insurgents had arrived in two speedboats to attack Mocimboa da Praia from the east while others attacked by land, overwhelming the army.

Islamist insurgents captured the strategic northern Mozambique port town of Mocimboa da Praia on Monday, their biggest prize in a 30-month-long insurgency, according to security sources and the official news agency.

The insurgents attacked by land and sea before dawn and overran the town and its military base, according to security sources and the official news agency AIM. It reported the spokesperson for the General Command of the Mozambican police, Orlando Mudumane, as telling reporters in Maputo that the terrorists had attacked the barracks of the defence forces, where they had hoisted their flag.

Mudumane said the insurgents had thrown up barricades on the main roads leading into the town, which they fully controlled.

The town is in Mozambique's northernmost Cabo Delgado province, about 200km north of the larger port town of Pemba and close to the Tanzanian border. Hundreds of soldiers and civilians have been killed in scores of attacks by the jihadist insurgency which began in October 2017.