The terrorists have killed more than 1,500 people in northern Mozambique and displaced more than a quarter of a million since 2017.
The southern Africa country has been overrun by militants in recent years.
Back in August, ISIS militants captured the port town of Mocimboa da Praia, in the province of Cabo Delgado, and told locals it would be their new capital.
The region is rich in oil – featuring Total and Exxon Mobile bases – and its deep forests offer terrorists smuggling routes for arms and ammunition.
Locals refer to the armed group as the Machababos or Al Shabaab, but the ISIS-affiliated group calls itself Al-Sunnah Wa Jama’ah.
David Otto, counter-terrorism and organised crime expert at Global Risk International, told Daily Star Online: “The complex terrain of deep forest and easy access to the Indian ocean makes the province of Cabo Delgado and the district of Mocimboa da Praia perfect for any armed group to hide.
“They can launch hit and run ambush tactics, escape to the high-sea to neighbouring states and an ideal logistics route for smuggling of illegal goods, arms and ammunition.”
Mr Otto claims that one of the terror group’s leaders, Abdala Likongo, is married to a member of the local Makunde tribe.
He added: “This local affiliation, support and knowledge of the people and the terrain provides the jihadist group with a huge advantage over government forces often deployed from outside the region with very little cultural intelligence and knowledge of the area.”
The terrorists pledged allegiance to ISIS last year and have launched a series of attacks.
The town is close to a site of natural gas projects worth £45billion.
Mr Otto continued: “Observers believe the Machababos have amassed a considerable fighting force and equipment like satellite phones, network computers and other necessary battlefield gadgets to withstand the Mozambique military forces.
“The group demonstrates a semi-organised structure with the capacity and skill to plan locally, launch surprise raids, steal weapons and use complex military-grade arms and ammunitions, from local police stations, military post and private security firms in the battlefield.”
It has reportedly recruited foreign fighters from neighbouring Kenya, Tanzania, and possibly Somalia.
Some estimates suggest they may have approximately 1,000 trained male fighters – but this could be a low estimate.
In March, jihadis occupied the centre of Mocimboa da Praia and burned government facilities.
They also launched an attack on a police headquarters in a second town, brandishing an ISIS flag.
Describing how they strike fear into their enemies, Mr Otto explained: “State forces and suspected spies have been captured and beheaded by the jihadist group to send a warning message.
“Women have been the subject of targeted kidnapping. Sources say the jihadists keep the women as sex slaves.”
Others “are sent for hard labour in jihadist owned fields as punishment”.
While they have not imposed their own laws on the local populations – as ISIS did at the height of its powers – there are fears the jihadis are unofficially collecting taxes from mining firms to fund themselves.
Mozambique ranks 181 out of 187 countries in the most recent United Nations Development Programme Human Development Index.
Terrorists have exploited the country’s poverty to entice desperate recruits.
Local security forces have struggled to contain the insurgency, and foreign mercenaries have also been massacred.