On the scorching edge of the Sahara Desert, the US Air Force is building a base for armed drones, the newest front in America's battle against the growing extremist threat in Africa's vast Sahel region.Three hangars and the first layers of a runway command a sandy, barren field. Niger Air Base 201 is expected to be functional early next year. The base, a few miles outside Agadez and built at the request of Niger's government, will eventually house fighter jets and MQ-9 drones transferred from the capital Niamey. The drones, with surveillance and added striking capabilities, will have a range enabling them to reach a number of West and North African countries.Few knew of the American military's presence in this desperately poor, remote West African country until October, when an ambush by Islamic State group-linked extremists killed four US soldiers and five Nigeriens.The $110 million project is the largest troop labour construction project in US history, according to Air Force officials. It will cost $15 million annually to operate.Citing security reasons, no official will say how many drones will be housed at the base or whether more US personnel will be brought to the region. Already the US military presence here is the second largest in Africa behind the sole permanent US base on the continent, in the tiny Horn of Africa nation of Djibouti.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. The drones at the base are expected to target several different al-Qaida and Islamic State group-affiliated fighters in countries throughout the Sahel, a sprawling region just south of the Sahara, including the area around Lake Chad, where the Nigeria's Boko Haram insurgency has spread.As the US puts drones at the forefront of the fight against extremists, some worry that civilians will be mistaken for fighters."We are afraid of falling back into the same situation as in Afghanistan, with many mistakes made by American soldiers who did not always know the difference between a wedding ceremony and a training of terrorist groups," said Amadou Roufai, a Nigerien administration official.Civic leader Nouhou Mahamadou also expressed concerns."The presence of foreign bases in general and American in particular is a serious surrender of our sovereignty and a serious attack on the morale of the Nigerien military," he said.The number of US military personnel in Niger has risen over the past few years from 100 to 800, the second largest concentration in Africa after the 4 000 in Camp Lemonnier in Djibouti. About 500 personnel are working on the new air and drone base and the base camp is marked with an American and Nigerien flag.Widespread poverty Intelligence, surveillance and reconnaissance are crucial in the fight against extremism, U.S. Africa Command spokesperson Samantha Reho said."The location in Agadez will improve US Africa Command's capability to facilitate intelligence-sharing that better supports Niger and other partner nations, such as Nigeria, Chad, Mali and other neighbours in the region and will improve our capability to respond to regional security issues," Reho said.The intelligence gathered by the drones can be used by Niger and other US partners for prosecuting extremists, said Commander Brad Harbaugh, who is in charge of the new base.Some in Niger welcome the growing US military presence in the face of a growing extremist threat in the region."Northern Mali has become a no man's land, southern Libya is an incubator for terrorists and north eastern Nigeria is fertile ground for Boko Haram's activities. Can Niger alone ensure its own security? I think not. No country in the world can today alone fight terrorism," said Souleymane Abdourahmane, a restaurant promoter in the capital, Niamey.Threats include al-Qaeda-linked fighters in Mali and Burkina Faso, Islamic State group-affiliated fighters in Niger, Mali and Nigeria and the Nigeria-based Boko Haram. They take advantage of the vast region's widespread poverty and countries' often poorly equipped security forces.Ít's no big deal to us'Foreigners, including a German aid worker kidnapped this month in Niger, have been targeted as well.The US military's use of armed drones comes as its special forces pull back from the front lines of the fight. The focus is changing to advising and assisting local partners higher up the chain of command, said US Special Command Africa commander Major General Marcus Hicks.Ibrahim Maiga, a Mali-based researcher for the Institute for Security Studies, said more needs to be known about the US military presence in the region."The US military footprint in the Sahel is difficult to grasp, just as it is not easy to assess its effectiveness," he said. "There isn't nearly enough information in the public space on this presence."Mud homes line the barbed wire fence at the edge of the main airport in Agadez. Residents watch the US forces come and go with curiosity.Shebu Issa, an assistant at a Quranic school, stood in one doorway as goats and children roamed the sandy roads."It's no big deal to us, they come and they don't bother us. We appreciate they want to help in the fight," he said. "We live a hard life, and don't make much money, so we hope maybe this will help us get more."