CAIRO — When a new bout of fighting between rival militias engulfed the Libyan capital in recent days, badly shaking the fragile United Nations-backed government, some combatants picked up rifles and rocket launchers and headed into the streets.
Others logged on to Facebook.
As rockets rained on parts of Tripoli, hitting a hotel popular with foreigners and forcing the airport to close, and 400 prisoners escaped from a jail, a parallel battle unfolded online. On their Facebook pages, rival groups issued boasts, taunts and chilling threats — one vowing to "purify" Libya of its opponents.
Some "keyboard warriors," as Facebook partisans are known in Libya, posted fake news or hateful comments. Others offered battlefield guidance. On one discussion page on Thursday, a user posted maps and coordinates to help target her side's bombs at a rival's air base.
"From the traffic light at Wadi al Rabi, it is exactly 18 kilometers to the runway, which means it can be targeted by a 130 mm artillery," the user, who went by the handle Narjis Ly, wrote on Facebook. "The coordinates are attached in the photo below."
Social media enjoys outsize influence in Libya, a sparsely populated yet violently fractured country that is torn by a plethora of armed groups vying for territory and legitimacy. They battle for dominance on the streets and on smartphones.
But Facebook, by far the most popular platform, doesn't just mirror the chaos — it can act as a force multiplier.
Armed groups use Facebook to find opponents and critics, some of whom have later been detained, killed or forced into exile, according to human rights groups and Libyan activists. Swaggering commanders boast of their battlefield exploits and fancy vacations, or rally supporters by sowing division and ethnic hatred. Forged documents circulate widely, often with the goal of undermining Libya's few surviving national institutions, notably its Central Bank.
Facebook is coming under scrutiny globally for how its platform amplifies political manipulation and violence. In July, the company began culling misinformation from its pages in response to episodes in Sri Lanka, Myanmar and India where online rumors led to real-life violence against ethnic minorities.
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On Wednesday, Facebook's chief operating officer, Sheryl Sandberg, will defend the company's efforts to limit disinformation and hate speech before the Senate Intelligence Committee, where she will testify along with Jack Dorsey, Twitter's chief executive.
Facebook insists it is assiduously policing its raucous Libyan platform. It employs teams of Arabic-speaking content reviewers to enforce its policies, is developing artificial intelligence to pre-emptively remove prohibited content, and partners with local organizations and international human rights groups to better understand the country. A spokeswoman said: "We also don't allow organizations or individuals engaged in human trafficking or organized violence to maintain a presence on Facebook."
Still, illegal activity is rife on Libyan Facebook.
The New York Times found evidence of military-grade weapons being openly traded, despite the company's policies forbidding such commerce. Human traffickers advertise their success in helping illegal migrants reach Europe by sea, and use their pages to drum up more business. Practically every armed group in Libya, and even some of their detention centers, have their own Facebook page.
Facebook removed several pages and posts after The New York Times flagged them to the spokeswoman on Sunday. But others remained.
"The most dangerous, dirty war is now being waged on social media and some other media platforms," Mahmud Shammam, a former information minister, said last week as fighting ripped through the Tripoli suburbs. "Lying, falsifying, misleading and mixing facts. Electronic armies are owned by everyone, and used by everyone without exception. It is the most deadly war."
Mr. Shammam made his declaration, naturally, on Facebook.