Djapo Mario, a 43-year-old salesman, woke up to the sound of gunfire as armed fighters attacked Mocimboa da Praia, a town in Mozambique's northern Cabo Delgado province and its military headquarters.

"We started to hear gunshots. They [attackers] were in confrontations with the police. They raided a police barracks and put their flag on it. We had to stay home and hide," Mario told Al Jazeera.

The assailants destroyed houses, vandalised public spaces, and erected barricades along important roads. It was unclear how many people were killed or wounded as most residents were still in hiding, and the government had yet to assess the situation.

The attackers were in control of the city until late on Monday when Mozambican authorities said the fighters were dislodged.

But residents are still in shock and trying to come to terms with the attack.

"It seems that things are calmer today [Tuesday] but the fear remains. I'm afraid to go to work, but I'm a trader and I depend on it to feed my family. I have two children aged five and six years," said Mario.

"We are afraid. It seems that this part is not Mozambique. We are dying and nobody does anything. We were at the government headquarters and there are not many agencies here to help us," he added.

"I'm still here. I have nowhere to go."

Increasing attacks

The commander of Mozambican police, Bernadino Rafael, called for calm.

"The defence and security forces are doing everything to restore order in Mocimboa da Praia. We ask people to remain calm," he told journalists in the capital, Maputo.

This was the most daring attack on Mocimboa da Praia, 90km (56 miles) from a major liquified natural gas project worth about $60bn.

Monday's attack was one of several in Cabo Delgado claimed by a shadowy armed group, Ahlu Sunnah Wa-Jama, or "followers of the prophetic tradition".

The group has killed hundreds and displaced thousands since it launched attacks in October 2017, according to medical charity Doctors Without Borders (Medecins Sans Frontieres, or MSF).

More recently, the armed group ISIL (ISIS) has claimed responsibility via its media outlets, though there has been no independent confirmation of a link.

Ahlu Sunnah Wa-Jama's attacks were initially dismissed as isolated acts of banditry, but the frequency of assaults has been increasing.

Ryan Cummings, a political and security risk analyst, said: "The increase in the attacks is reflective of the failure of the state to adequately curtail the Islamist insurgency."

"The militant group has also employed enhanced weaponry and demonstrated evolved tactical engagement," he told Al Jazeera.

'Because of the gas'

The northern region of Mozambique is home to one of the world's biggest recent gas finds, where Exxon Mobil Corp, Total, and other energy firms have set up operations.

"It looks like this war is taking place because of the gas. If so, I prefer that we don't have gas to live safely," Mario said.

Recently, Exxon and Total called for more troops to guard their facilities in the north.

Government forces have struggled to contain the attacks despite promises by President Filipe Nyusi to stem the violence after he was sworn in for a second five-year term in January.

"Although extremist attacks have not led to any direct acts of violence against interests associated with the liquefied natural gas industry, it is likely to heighten concerns regarding the threat posed by militants to the nascent sector," Cummings said.

"The state security services will have to prioritise between the Cabo Delgado insurgency, the armed threat posed by the Renamo military junta, post-cyclone reconstruction, and any measures which will be implemented in the country in light of the detection of COVID-19 within Mozambican borders," he added.

Forced displacement

About 100,000 people have been displaced because of the surge of attacks in Cabo Delgado province over the last two years, according to the United Nations's human rights body. Many have fled to islands with little infrastructure.

Rights group Amnesty International has called on the government to step up efforts to protect civilians from further attacks.

"We are not aware of measures put in place to look after those who have been displaced by the attacks, as the government doesn't acknowledge the problem. NGOs are not allowed into the conflict area," David Matsinhe, Amnesty's researcher for Southern Africa, said.

"There are allegations of human rights violations such as extrajudicial killings of innocent civilians accused of aiding abetting the insurgents. The government does not want embarrassing information - such as about this attack - to surface because such information would betray the government's weakness, inability to control the situation," Matsinhe added.