NAIROBI — The website’s headlines trumpet al-Shabab’s imminent demise and describe an American jihadist fretting over insurgent infighting. At first glance it appears to be a sleek, Horn of Africa news site. But the site — sabahionline.com — is run by the US military.

The site, and another one like it that centers on northwest Africa, is part of a propaganda effort by the US military’s Africa Command aimed at countering extremists in two of Africa’s most dangerous regions — Somalia and the Maghreb.