GULU, Uganda - A prominent red sign welcoming visitors to this remote and dusty agricultural city makes the announcement in capital letters: "This is now a 4G zone."

That is thanks in part to Facebook Inc., which, along with Indian telecom giant Bharti Airtel Ltd.'s Ugandan unit and Mauritius-based Bandwidth & Cloud Services Group, laid nearly 500 miles of fiber-optic cable across the isolated northwest of this East African nation. The project, begun in early 2017 and completed at the end of last year, has expanded the region's network capacity, providing faster internet access to an area with some three million people, many of whom live in towns still haunted by memories of the three-decade insurgency led by Joseph Kony's Lord's Resistance Army.

The Ugandan cable is the largest terrestrial network Facebook has helped construct in Africa and part of what the company describes as a broader push to connect the approximately 3.8 billion people who are still without internet around the world. The move comes as Facebook's user growth slows in developed markets like the U.S. and Europe.