"We have blocked some websites as there were serious national security concerns," said a government official.
The websites include popular video sharing platforms like DailyMotion and Vimeo. Some have reportedly been allowed to resume after the allegedly objectionable content was removed.
The government said some websites had material about Areeb Majid, an alleged ISIS member who was arrested by the National Investigation Agency or NIA.
Sources said the government felt the sites were being used to induce Indian youth to join ISIS and to spread news about purported deaths of people fighting Allied Forces in countries like Afghanistan and Iraq.
The head of the ruling BJP's IT Cell, Arvind Gupta, also said that the websites were blocked on the advice of the anti-terror squad.
"The websites were blocked after an advisory by Anti Terrorism Squad, which said these had anti-India content from ISIS," Mr Gupta said in a tweet.
The sites that have removed objectionable content and cooperated with the police have been unblocked, he added.
A list of 32 websites in what was purported to be a Department of Telecom circular went viral on the micro-blogging site Twitter.
While there was no official word from the IT ministry, sources in the department confirmed that there was such a circular.
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