HARARE, Zimbabwe — A woman from Bridgewater faces 20 years in prison over a Twitter post about the president of Zimbabwe.

Martha O'Donovan, 25, was in court on Saturday morning for her tweet that called President Robert Mugabe a "sick man." The tweet included a picture showing the 93-year-old with a catheter. The government claims the message represents an attempt to undermine the authority of Mugabe.

She was arrested on Friday at her home in Harare, the African nation's capital city.

O'Donovan is from the Martinsville section of Bridgewater, according to her Facebook page, and a graduate of Bridgewater-Raritan Regional High School.

The New York University graduate works for the Magamba Network, a network working to bring change the political situation Zimbabwe using, according to its website, "new media, activism and innovation."

Earlier this year, she presented a talk at a Re:Publica digital culture conference on "How Zimbabweans Rebel Online."

She also manages a pop-up bar called Mar's Bar.

A lawyer for O'Donovan, Rose Hanzi, told the court that her arrest was illegal because police did not explain the reasons for it. The arresting officer was being questioned in court.

The charge of subversion carries up to 20 years in prison. O'Donovan also is charged with undermining the authority of or insulting the president

O'Donovan has denied the allegations as "baseless and malicious."

It was the first arrest since Mugabe last month appointed a cybersecurity minister, a move criticized by activists as targeting social media. Zimbabwe was shaken last year by the biggest anti-government protests in a decade. Frustration is growing in the once-prosperous southern African nation as the economy collapses and the president, in power since 1980, is already running for next year's elections.

The group representing O'Donovan, Zimbabwe Lawyers for Human Rights, says it has represented nearly 200 people charged for allegedly insulting Mugabe, the world's oldest head of state, 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," said Amnesty International's deputy regional director, Muleya Mwananyanda. The statement said Zimbabwe authorities tracked tweets to O'Donovan's IP address.

The Associated Press contributed to this report