In Bengaluru, protesters holding signs were shunted away by police after authorities.
Indian authorities on Thursday clamped down on demonstrations against a contentious citizenship law, invoking a measure to prohibit public gatherings in two states and parts of the nation's capital, together home to more than 260 million people.
A coalition of civil society groups called for rallies across the country on Thursday to voice opposition to the law, which opponents say is discriminatory and violates India's constitution. The law creates a fast-track to citizenship for migrants from six religions who arrived in India by 2014, but excludes Muslims.
In Delhi, hundreds of peaceful protesters gathered near one of the city's major monuments to begin a march, but police imposed a measure that forbids gatherings of four or more people, effectively making protests illegal. Police detained protesters and took them away in buses.
Internet service was also suspended in some parts of the city, said an employee of a cellular company who spoke on the condition of anonymity because she was not authorized to discuss the matter. India leads the world in the number of Internet shutdowns, which authorities say are a way to prevent violence and unrest.
Protests have erupted against the law in recent days and some have turned violent. On Sunday, police stormed a university campus in Delhi, striking unarmed students and firing tear gas into the library. The protests are the most sustained show of opposition to Indian Prime Minister Narendra Modi since he came to power in 2014.
In Bangalore, the capital of the state of Karnataka, protesters holding signs were shunted away by police after authorities invoked the same measure, known as Section 144, to disallow public gatherings. Among those detained was Ramachandra Guha, one of India's most distinguished historians.
"This is totally wrong," he said in a video from the scene. "Our paranoid rulers in Delhi are scared" of a peaceful protest.
All of Uttar Pradesh, India's largest state and home to 200 million people, was placed under Section 144 restrictions on Thursday. The state's director-general of police, O.P. Singh, told reporters that no protest would be permitted in the state.
"Parents are advised to counsel their kids and ask them not to participate in any kind of protest, and if they do, police will take action against them," he said.
In Delhi, authorities shut down more than 15 subway stations, snarling transportation. Police set up barricades close to the site of the planned protest at the city's Red Fort, making it difficult to reach.
The citizenship law is "unconstitutional," said 24-year-old student Swati Khanna, 24, before she was taken away by police officers. "India is becoming a police state but we will reclaim it."
Further protests were expected elsewhere in the country later on Thursday, including in the eastern city of Kolkata and in the financial capital, Mumbai. The governments of those cities' respective states, West Bengal and Maharashtra, are not controlled by PM Modi's Bharatiya Janata Party, and local authorities have allowed the demonstrations to proceed.