NEW DELHI: India has partially revoked an order to block hundreds of pornographic websites following an uproar on social media, but the government ordered Internet service providers to shut down sites that promote child pornography.

The government last week asked operators to block access to 857 adult websites on grounds of morality and decency, resulting in an angry backlash on Twitter and a debate about censorship in the world's largest democracy.

Service operators will now need to unblock most of those sites but will still disable those that promote child pornography, a spokesman for India's department of telecoms said on Wednesday.

The revised order is drawing the ire of service providers, who have been effectively asked to check and decide which sites need to be blocked.

“This whole thing is very ambiguous. How are we supposed to check if the sites have child porn?” said an official at one of India's main telecom operators.

“Is this what we are supposed to do now?” the exasperated executive said, referring to having to check sites for child pornography.

Censorship of Internet content is common in India but the order to block the 857 adult sites was the first big crackdown on Internet pornography.

In 2011, India urged social network companies to screen content and remove offensive material. A year later, the government faced criticism for ordering dozens of Twitter accounts to be blocked for spreading rumours.

Use of social media and smartphones is rising rapidly in the country and pornography is in demand: Pornhub, an adult website, last year said India ranked fifth for daily visitors.