(Bloomberg) -- India’s top court has extended the house arrest of a group of activists and lawyers who were swept up in a nationwide police operation that human rights groups have said was aimed at intimidating critics of the government.

The Supreme Court ordered their home detention to continue for another month.

The action comes amid growing concerns about rising nationalism and a crackdown on dissident voices ahead of general elections next year. Other activists and academics had challenged the arrests with a public interest litigation at the Supreme Court of India.

The court had previously ordered that the five be kept under house arrest and not transferred into police custody. Justice Dhananjaya Y. Chandrachud -- one of those hearing the case -- said: "Dissent is the safety valve of democracy. If you don’t allow the safety valve, the pressure cooker will burst."

Maoist Groups

Those arrested are known for their work with India’s marginalized tribal and lower caste communities, and other activists said they’d been rounded up for criticizing the government. In a previous joint statement, Amnesty International India and Oxfam India said the crackdown and arrests "raise disturbing questions about whether they are being targeted for their activism."

Left-wing academics and intellectuals, particularly those who work with India’s tribal communities, are often accused of supporting Maoist groups that oppose industrial development and launch attacks on Indian security forces. For decades, Maoists have regularly attacked paramilitary troops and police, mainly in rural parts of the country’s poorer central-eastern states.

To contact the reporters on this story: Upmanyu Trivedi in New Delhi at utrivedi2@bloomberg.net;Iain Marlow in New Delhi at imarlow1@bloomberg.net

To contact the editors responsible for this story: Ruth Pollard at rpollard2@bloomberg.net, Arijit Ghosh

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