The lawsuit, filed in Kenya on Tuesday, was brought by two Ethiopian researchers and a Kenyan human rights organisation, the Katiba Institute. It also has the support of the campaign group Foxglove.
It alleges Facebook's recommendations systems amplified violent posts in Ethiopia and identified several people as targets. The suit also said the company failed to exercise reasonable care in training its algorithms to identify dangerous posts and in hiring staff to police content for the languages covered by its regional moderation hub in Nairobi.
The lawsuit specifically pointed out several of the platform's posts, which directly preceded the murder of the father of one of the researchers. The posts were published in October 2021 and included the use of ethnic slurs to refer to Professor Meareg Amare Meareg. They included the man's address and called for his death.
At the time, his son reported the content, but the company "left these posts up until it was far too late", he has claimed.
"If Facebook had just stopped the spread of hate and moderated posts properly, my father would still be alive," Meareg said.
In a sworn statement filed with the court, Meareg alleged the Facebook's algorithm promotes "hateful and inciting" content because it is likely to draw more interaction from users. He also criticised the company's content moderation in Africa as "woefully inadequate" and unable to deal with the volume of posts in key languages Amharic, Oromo and Tigrinya.
The plaintiffs are asking the court to order Meta to take emergency steps to demote violent content and increase moderation staff in Nairobi. In addition, they have demanded $2bn (£1.6bn) from the social media company, which would be used to create a fund for victims of hate on Facebook.
Over the last two years, Ethiopia has been suffering from a bloody civil war that has killed hundreds of thousands of people as a result of clashes between the Ethiopian government and forces in the northern Tigray region. Today, as many as 400,000 Ethiopians are said to be living in famine-like conditions.
Although a surprise peace deal was agreed on last month, there has been a recent upsurge in ethnically motivated killings between Amhara- and Oromo-speaking communities, which saw Meareg's father becoming one of the victims.
During the duration of the conflict, both parties have taken to social media platforms such as Facebook to gain support for their cause.
In response to the lawsuit, Meta spokesperson Erin McPike said that hate speech and incitement to violence were against the rules of Facebook and Instagram.
"We invest heavily in teams and technology to help us find and remove this content," McPike added. "We employ staff with local knowledge and expertise and continue to develop our capabilities to catch violating content in the most widely spoken languages in Ethiopia."
The company maintained that Ethiopia is a high priority and said it had taken key steps to prevent the spread of violent content, including reducing posts' virality, expanding violence and incitement policies and improving enforcement.
Last year, Meta's independent Oversight Board recommended a review of how Facebook and Instagram have been used to spread content that heightens the risk of violence in Ethiopia.
The case carries echoes of accusations Meta has faced for years involving atrocities stoked on its platforms, including in Myanmar, Sri Lanka, Indonesia and Cambodia. The company has acknowledged being "too slow" to act in Myanmar and other conflicts.
In 2021, whistleblower Frances Haugen, a former Meta employee, told the US Senate the platform's algorithm was "fanning ethnic violence... picking up the extreme sentiments, the division" in Ethiopia, as those posts attracted high engagement.
