A U.S. citizen was charged with attempting to overthrow the Zimbabwean government via Twitter. Police accused her of insulting 93-year-old President Robert Mugabe in a tweet. (Reuters)

In 2016, Martha O'Donovan, a 25-year-old New York University graduate, moved to Zimbabwe.

She got a job with Magamba TV, located in Harare. It's a satirical comedy station, and O'Donovan was a manager and “media activist.”

Now, she's in jail.

At issue: a tweet attacking Zimbabwean President Robert Mugabe. In it, the president is called a "sick and selfish man."

The tweets come from the account of @matigary, who joined Twitter in February 2016. Zimbabwe authorities say they believe O'Donovan is the author of the tweet based on her IP address. But O'Donovan has denied this, and @matigary has continued to tweet since O'Donovan was jailed.

She has been charged with subversion and attempting to overthrow the Mugabe government. That charge carries a sentence of up to 20 years in prison.

In a statement to the police, O'Donovan, who grew up in New Jersey, called the allegations “baseless and malicious.” Her lawyer, Rose Hanzi, has argued that the charge is illegal because the police did not inform O'Donovan of it when she was taken from her home Friday morning. Her bail hearing is set for Nov. 15.

The State Department says it is aware of O'Donovan's situation, but officials declined to comment further.

O'Donovan's arrest comes a month after Mugabe appointed a cybersecurity minister. When he was appointed, activists on social media worried that he would target them.

Zimbabwe Lawyers for Human Rights say at least 200 people have been charged for allegedly insulting Mugabe in recent years.

“This arrest marks the start of a sinister new chapter in the Zimbabwean government’s clampdown on freedom of speech, and the new battleground is social media,” Muleya Mwananyanda, Amnesty International’s deputy regional director, told the Associated Press.

“Most Zimbabweans do vent on social media about the state of the country, so if they arrest her for this, they might as well arrest all Zimbabweans on social media,” Munya Bloggo, an activist, told BuzzFeed News. “I don't think anyone is exempt.”

Tongia Makawa, the station's co-founder and project manager, told BuzzFeed News that he and his colleagues are still in shock. “In all honesty, I think the only thing that's separates her from the rest of the team is the fact that she's a foreign national,” he said.