One of Saudi Arabia’s most prominent exiled activists has quit Twitter and Facebook, saying that the social media giants have become tools for oppressive governments and trolls to harass and silence campaigners.

Manal al-Sharif, one of the leading figures in Saudi women’s long fight for the right to drive in their homeland, deleted her Twitter account live on stage at the SingularityU Nordic “global innovation” conference last week.

“Twitter is really a powerful tool, and its being used against us,” she said, before closing the account, which has nearly 300,000 followers. In a video posted the next day on YouTube, she said Twitter had saved her life as a campaigner in Saudi Arabia, but today had become a playground for mobs of “trolls, pro-government mobs and bots”, many paid for by oppressive governments.

“If the same tools we joined for our liberation are being used to oppress us and undermine us, and used to spread fake news and hate, I’m out of these platforms,” she said, adding she would continue to campaign, calling for the creation of more ethical social media.

Sharif, who left Saudi Arabia several years ago for self-imposed exile, and remains a prominent voice on human rights and feminism, said she had also deleted her Facebook account. Her protest comes at a time of increased concern about how social media has been used to spread disinformation, and intense debate about how companies should balance controls on abusive behaviour with stated commitment to free speech.

The Saudi government is among many autocratic regimes to have poured huge amounts of money and energy into creating a pro-government Twitter presence.

Inside Saudi Arabia, activists have been effectively silenced by several waves of detentions. Among those jailed are many of the other women who campaigned with Sharif for the right to drive, while Crown Prince Mohammed bin Salman tries to garner credit for the change.

But the brutal killing of dissident Jamal Khashoggi inside the Saudi consulate in Istanbul at the start of this month has highlighted the Saudi state’s determination to crush dissent beyond its borders.Sharif said online harassment was another face of that campaign, but vowed she would not be silenced.

“Twitter now is becoming a trap, and it’s being used in a very efficient way by those governments, dictatorships and tyrants to silence us, and not only that, to spread their own propaganda, their own hate speech, misinformation and disinformation,” she said.

“I’ll continue speaking up because tyrants and dictators are the ones who should be afraid, not us.”