Pastor Evan Mawarire, the founder of Zimbabwe's #ThisFlag social media movement, on Friday called for a protest against President Robert Mugabe and his government.
Mawarire asked his supporters in a Facebook video message to stand up and sing Zimbabwe's national anthem during a cricket match in the southern town of Bulawayo on Saturday.
Zimbabwe is scheduled to play New Zealand, and the game will be broadcast internationally.
"When the 36th over starts, you and I are going to stand up as a sign of saying for 36 years [of Mugabe’s rule] we have been quiet, but now we are standing up,” said the 39-year-old activist, who recently fled to neighbouring South Africa after receiving death threats.
"I want you to sing the national anthem. They can't shut you up. They can't arrest you for singing the national anthem," Mawarire said.
National army commander Lieutenant-General Philip Sibanda warned the military "was ready to deal with" those using social media to mobilise the population, the state-owned Herald newspaper reported Friday.
Sibanda described internet campaigns as "cyber warfare" against the government.
The ruling Zanu-PF party meanwhile said the protest action was a ploy by Mawarire "to achieve his political ambitions."
"If these people have issues, they must engage the government and not be confrontational," Tafadzwa Mugwadi, a senior Zanu-PF youth leader told dpa.
With the national flag wrapped around his neck, Mawarire, who doesn't belong to a political party, complained about the country's politics, economic demise and corruption in a video posted on his Facebook account in early May.
The video went viral under the hashtag #ThisFlag. On July 6, tens of thousands of #ThisFlag supporters shut down the capital by striking.
Mawarire was arrested and charged with attempting to overthrow the government, but later released due to a technicality.