Zimbabwe human rights campaigner Jestina Mukoko has been ordered back to jail for plotting to topple President Robert Mugabe, her lawyer said.
Ms Mukoko is among 18 leading activists to be detained just two months after they were released on bail.
The activists say they were tortured into making false confessions.
The party of Prime Minister Morgan Tsvangirai has warned that the move could threaten the future of Zimbabwe’s power-sharing government.
“Today’s ruling seriously threatens not only the life and health of the inclusive government, but its longevity and durability,” a statement from the Movement for Democratic Change (MDC) said.
It added that the decision “threatens the goodwill” Zimbabwe has received from the international community.
Magistrate Catherine Chimanda in Harare said she was revoking bail because a formal indictment had been filed a day earlier.
It accuses Ms Mukoko and the others of sabotage, terrorism and banditry.
The suspects – who include several MDC members – were detained in December for three months.
They were charged with attempting to overthrow Mr Mugabe’s government and replace it with one headed by Mr Tsvangirai.
Some had fallen ill and were put under police guard in hospital.
Ms Mukoko, the director of the Zimbabwe Peace Project, was granted medical treatment at a previous court hearing after she said she had been tortured.
The latest detentions will be seen as another blow to the authority of Zimbabwe’s new power-sharing government, which has been struggling to resolve a plethora of political and economic issues, says the BBC’s Southern Africa correspondent, Peter Biles.