About 42,000 people are on the verge of starving to death in northeast Burkina Faso as Islamist militants lay siege to towns and villages, an International Rescue Committee official said.

About 800,000 people are trapped in the settlements, most notably in Djibo, which has largely been cut off from the outside world for more than a year, said Modou Diaw, regional vice president for the IRC in West Africa. In that town, which Diaw traveled to by helicopter this month, 360,000 people are sheltering, with 75% of those being refugees from elsewhere in the country.

“People are already dying of hunger,” Diaw said in an interview. “If nothing is done, it can be much worse.”

Djibo is one of the most stark examples of how rising insecurity, coupled with climate change, has left millions of people displaced and hungry across swathes of West Africa’s Sahel region. The 42,000 are classified as IPC 5, a technical term that refers to people suffering from famine. Millions more are suffering from less severe food insecurity.

In Djibo, convoys have stopped transporting food and other goods by road to the town after constant attacks and what was once one of the biggest cattle markets in the Sahel is now largely deserted, Diaw said. Fields on the outskirts of the city cannot be tended because of the militants.

“I spent two or three hours in Djibo without seeing one sheep or goat,” Diaw said. “There is nothing.”

Across the central Sahel - which consist of Burkina Faso, Mali and Niger - the number of people in need of humanitarian assistance has almost tripled to more than 16 million people, the IRC said in a June report.

The number of people suffering from severe food insecurity has risen more than sixfold since 2014 to 5.4 million people and the number of displaced people has jumped almost 25-fold to nearly 3 million people.