India's government has authorised the prosecution of 21 internet firms, including Facebook, Yahoo! and Google, in a case over obscene content posted online, sources say.

The approval could lead to company directors being called to a trial court in New Delhi to answer serious charges such as fomenting religious hatred and spreading social discord, an official and a lawyer said.

A file photo of an online cartoon of Savita Bhabhi which proved a taboo too far Indian government censors.

A criminal case against the web titans was first filed in a lower court by local journalist Vinay Rai, who complained that the sites were responsible for obscene and offensive material posted by users.

He also claimed they had broken laws designed to maintain religious harmony and "national integration" in India.