Portugal said on Friday it would help Mozambique train up security forces to tackle a wave of militant attacks in the north of the African nation.

Violence had surged this year in Mozambique's Cabo Delgado - a region that borders Tanzania and is home to natural gas developments worth about $60 billion.

"What we are going to do is to support Mozambican authorities so that they can exercise their sovereignty," Portuguese Defence Minister Joao Gomes Cravinho said during a trip to his country's former colony.

Cravinho told Lusa news agency a Portuguese team would work with Mozambique's government from next month to draw up a strategy to train local soldiers, marines and other forces.

Mozambique had already asked the European Union for help in training its forces to battle the insurgency, which has alarmed countries across southern Africa and beyond and forced hundreds of thousands of people to flee their homes.

Cravinho said Portugal, which takes over the presidency of the European Union in January, would support Maputo's request.

Nathan Sales, the Coordinator for Counterterrorism at the U.S. State Department, said last week the insurgents in northern Mozambique belonged to a "committed" affiliate of Islamic State and should be seen as a global terrorism threat.