Mozambique has officially started exporting liquefied natural gas (LNG) produced in the country's restive north, President Filipe Nyusi said on Sunday.

Nyusi said Mozambique was entering "the annals of world history" as the first shipment of gas produced at the offshore Coral Sul plant, managed by Italian company Eni, was leaving territorial waters.

"It is with great honor that I announce the start of the first export of liquefied natural gas," Nyusi said in a video statement.

A tanker, the "British Sponsor," was leaving Mozambican waters for the international market, the president said.

"Today, Mozambique enters the annals of world history as one of the exporting countries of LNG," said Nyusi.

Mozambique has set high hopes on vast natural gas deposits – the largest ever found south of the Sahara – that were discovered in the northern Cabo Delgado province in 2010.

Once tapped, Mozambique could become one of the world's 10 biggest exporters.

But the region has since been hit by an insurgency waged by a Daesh-affiliated militant group that has cast doubts over the viability of LNG exploration sites, and stalled progress.

The conflict has killed more than 4,100 people over the past five years, according to conflict watchdog ACLED.

Hundreds of thousands more have been displaced, the United Nations says.