An amendment to India's Information Technology Act in 2009, which was championed by minister Kapil Sibal, makes it illegal to make "grossly offensive" comments online, a measure seen by critics as a draconian limit on free speech. 

Two girls were arrested earlier this month by police in the commercial capital Mumbai over comments on Facebook which questioned the shutdown of the city for the funeral of local hardline politician Bal Thackeray. 

The personal website of Sibal, who has promised to review some sections of the law, was out of order on Friday and the hackers, thought to be from the Anonymous India collective, also defaced the site. 

The "About" section of the website described Sibal as "Born with a below-60 IQ he thought he could mess with the Internet and let the elite of his party suppress freedom of speech," India's Computer World magazine reported. 

The Twitter account of Anonymous India (@opindia_revenge) announced that Sibal's site had been "trolled" by hackers who had posted comments and edited photos. 

India's Supreme Court has accepted a petition to examine the legality of section 66A of the IT Act which makes sending information of "grossly offensive or menacing character" punishable with up to three years in jail. 

On Friday, India's top court directed the state government in Maharashtra, of which Mumbai is the capital, to explain the circumstances under which police arrested the two girls over their Facebook comments. 

The government has since issued guidelines on enforcing the law, but a long-standing campaign against it has gathered pace and the Supreme Court may also strike it down as unconstitutional. 

The arrest of an anti-government cartoonist on a sedition charge in October also raised concerns about the limits on freedom of speech in the world's biggest democracy. 

Calls by AFP to Sibal's office were not answered.