NEW DELHI — Vernon Gonsalves, a rights activist, was preparing for his morning bath when the police banged on his front door. Officers rummaged through his home in Mumbai for nearly eight hours, confiscating books, his laptop, a hard drive and pen drives — and then arrested him.

“My dad’s phone was seized, and our phones were put on flight mode so people trying to contact us could not,” the activist’s son, Sagar Abraham-Gonsalves, said in an interview. “They did not ask us a lot of questions. They just kept raiding, pulling out books and academic works.”

Across India on Tuesday, from New Delhi to Hyderabad to Ranchi, police officers carried out similar raids on the homes of at least a half-dozen activists, writers and lawyers. All were known for supporting resistance movements and marginalized groups, or for speaking out against the government.

Five people, including Mr. Gonsalves, were taken into custody on suspicion of abetting communist groups, plotting the assassination of top government officials and inciting a large riot this year. Several other activists arrested in June have been accused of similar crimes.