Using a freedom of information law, the Center for Internet and Society, a Bangalore-based research and advocacy group, recently obtained and published a list of 11 Web sites banned by the Department of Information Technology. Other government agencies have probably blocked more sites, the group said.

The new Internet rules go further than existing Indian laws and restrictions, said Sunil Abraham, the executive director for the Center for Internet and Society. The rules require Internet “intermediaries” — an all-encompassing group that includes sites like YouTube and Facebook and companies that host Web sites or provide Internet connections — to respond to any demand to take down offensive content within 36 hours. The rules do not provide a way for content producers to defend their work or appeal a decision to take content down.

“These rules overly favor those who want to clamp down on freedom of expression,” Mr. Abraham said. “Whenever there are limits of freedom of expression, in order for those limits to be considered constitutionally valid, those limits have to be clear and not be very vague. Many of these rules that seek to place limits are very, very vague.”

An official for the People’s Union for Civil Liberties, an advocacy group based in New Delhi, said on Wednesday that it was considering a legal challenge to the constitutionality of the new rules.

“What are we, Saudi Arabia?” said Pushkar Raj, the group’s general secretary. “We don’t expect this from India. This is something very serious.”

An official at the Department of Information Technology, Gulshan Rai, did not return calls and messages.

The rules are based on a 2008 information technology law that India’s Parliament passed shortly after a three-day siege on Mumbai by Pakistan-based terrorists that killed more than 163 people. That law, among other things, granted authorities more expansive powers to monitor electronic communications for reasons of national security. It also granted privacy protections to consumers.