The Department of Telecommunications has issued orders for the blocking of 857 websites serving pornography, said two persons familiar with the matter, who declined to be named.
Section 69 (A) of India's Information Technology Act allows the government to order blocking of public access to websites and other information through computer resources, though this section appears to be designed to be invoked when a threat is perceived to the sovereignty and integrity of India, security of the state, friendly relations with foreign states or public order.
"The government cannot on its own block private access to pornography under current statutes," said Pranesh Prakash, policy director of the Centre for Internet and Society in Bangalore. "Parliament has not authorized the government to ban porn on its own."
"However, courts have in the past ordered specific websites to be blocked for specific offences such as defamation, though as far as I know not for obscenity," Prakash added.
Viewing pornography privately is not a crime in the country, though its sale and distribution is an offense.
Some porn websites were still accessible through certain Internet service providers on Monday, as some ISPs took some time to implement the order. "All the 857 websites will be blocked by all ISPs today," said a source in the ISP industry, who requested anonymity. "As licensees we have to follow the orders."
The government could not be immediately reached for comment.
Reports of the blocks created a furore among Internet users in the country, who criticized the move on Reddit, Twitter and other social media.
India's Supreme Court struck down in March as unconstitutional an Internet law that provided for the arrest of people sending online messages considered offensive or menacing. But it upheld Section 69 (A) in that same ruling, which it described as a "narrowly drawn provision" limited to a few subjects.
In a public interest lawsuit on the blocking of pornography, the Supreme Court last month declined to issue an interim order that would block porn websites at the request of the private litigant, according to a report.
John Ribeiro covers outsourcing and general technology breaking news from India for The IDG News Service. Follow John on Twitter at @Johnribeiro. John's e-mail address is john_ribeiro@idg.com