The Zimbabwe pastor who launched a social media campaign criticizing the government and then left the country for his safety is calling for a massive but peaceful uprising.

Evan Mawarire told a cheering crowd at a South African university Thursday that Zimbabwe once was promising but had been reduced to “horror and unimaginable disappointment.”

Frustration has been growing in the southern African country amid a collapsing economy and allegations of corruption. People across the country earlier this month staged the largest anti-government strike in nearly a decade.

President Robert Mugabe, the world’s oldest head of state at age 92, says people who aren’t happy should leave the country.

Mawarire says Zimbabwe’s government “cannot deal with people that are genuinely peaceful,” and he calls on citizens to rewrite the country’s future.