LONDON - “What we saw in Myanmar and are now seeing in Ethiopia are only the opening chapters of a story so terrifying, no one wants to read the end of it,” Haugen said in her striking testimony.

Haugen warned that Facebook was “literally fanning ethnic violence” in places such as Ethiopia because it was not policing its service adequately outside the US.

About half of Myanmar’s population of 53 million use Facebook, with many relying on the site as their primary source of news. In June this year, an investigation by the rights group Global Witness found that Facebook’s algorithm was promoting posts in breach of its own policies that incited violence against protesters marching against the coup launched by the military in February.

Researchers began by liking a Myanmar military fan page, which was not seen to be violating Facebook’s terms. They found that Facebook then suggested several pro-military pages that did contain abusive content.

The link between social media posts and offline violence in Myanmar had already been widely documented.

In 2018 a Guardian analysis revealed that hate speech exploded on Facebook at the start of the Rohingya crisis the year before, when attacks by armed groups and ordinary communities on people from the Muslim minority erupted.

Thousands of posts by nationalist, anti-Rohingya supporters gained traction online, including posts which falsely claimed mosques were stockpiling weapons.

An independent investigation commissioned by Facebook later agreed with assessments that the site had been used to incite offline violence.