One of the plaintiffs says he contacted Facebook several times about posts threatening violence against his father, who was murdered by members of a militant group.
A newly formed rebel alliance led by the Tigray People's Liberation Front is within striking distance of Addis Ababa. A failed state could displace millions of people and stoke more ethnic violence.
An investigation released a year after the start of violence over the breakaway region of Ethiopia has compiled evidence of summary executions, torture and rape.
The conflict in northern Ethiopia's Tigray region began in early November. Thousands have died and close to 2 million people are reported to have been displaced.
