Militant group Islamic State has claimed responsibility for an attack in northern Mozambique just south of the site of gas projects worth US$60 billion being developed by the likes of Exxon Mobil and Total.

Insurgents attacked the town of Mocimboa da Praia on Monday, briefly occupying some areas and its army barracks before being pushed out on Tuesday, Mozambique authorities and security analysts said.

Islamic State claimed the attack through its Amaq news agency, which said dozens of soldiers and police officers had been killed or injured. The government has not provided a figure of dead or injured.

This violent escalation in Mocimboa da Praia is the culmination of a tragic failure by the Mozambican government to protect the people in this volatile area

Muleya Mwananyanda, Amnesty’s deputy director for east and southern Africa

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“Military sources told Amaq that Islamic State fighters attacked five army and police barracks in the town,” the agency said in Tuesday’s report, adding that weapons, ammunition and other equipment had also been seized.

Government spokesman Filimao Suaze said the retreating attackers had left a “trail of destruction and dead bodies”, and that security had been beefed up in the area.

While Islamic State has claimed a spate of recent attacks in the northernmost province of Cabo Delgado, home to the gas developments following one of the biggest gas finds in a decade off its coast, Tuesday’s claim of responsibility is the first matched by rare official confirmation of an attack.

The government does not acknowledge such claims, however.

Mocimboa da Praia, 60 kilometers south of the gas projects, previously served as the main airport for international workers flying into the developments and its port is used for cargo deliveries.

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Exxon and Total did not immediately respond to emailed requests for comment sent outside usual business hours.

NGOs say the government must do more to protect the mostly poor civilians in the area and step up transparency.

“This violent escalation in Mocimboa da Praia is the culmination of a tragic failure by the Mozambican government to protect the people in this volatile area,” said Muleya Mwananyanda, rights group Amnesty’s deputy director for east and southern Africa.

“For almost three years, armed groups have been attacking villagers around Cabo Delgado, causing untold human suffering without being held accountable.”

The organization said about 350 people have been killed since 2017, but many estimate a much higher figure. More than 900 people have been reported killed, says a non-government body, the Armed Conflict Location and Event Data project.