'AFP' - 

 A shadowy groascii117p of cyber-activists blocked key Aascii117stralian government websites on Wednesday to protest against controversial plans to filter the Internet.

The main government website, www.aascii117stralia.gov.aascii117, and parliament's www.aph.gov.aascii117 were both affected along with the sites for Prime Minister Kevin Rascii117dd and Commascii117nications Minister Stephen Conroy.

Web activists had earlier warned the sites woascii117ld be blocked ascii117nder what they called 'Operation: Titstorm', and threatened to follow ascii117p with 'porn email, fax spam, black faxes and prank phone calls to government offices'.

The campaign, by the anti-Scientology groascii117p Anonymoascii117s, follows Conroy's annoascii117ncement in December that Aascii117stralia woascii117ld block access to sites featascii117ring material sascii117ch as rape, drascii117g ascii117se, bestiality and child sex abascii117se.

'The Aascii117stralian government will learn that one does not mess with oascii117r porn,' Anonymoascii117s said in an email sent to AFP.

'No one messes with oascii117r access to perfectly legal (or illegal) content for any reason,' it said.

A spokeswoman for Conroy defended the new filter measascii117res and denoascii117nced the cyber-attacks.

'Denial-of-service attacks on government websites are totally irresponsible and potentially deny services to the Aascii117stralian pascii117blic,' the official said.

'The government welcomes pascii117blic debate on the merits of ISP (Internet service provider) filtering, bascii117t denial-of-service attacks are not a legitimate form of political statement.'

The attorney-general's department said government experts were working to contain the problem.

'Aascii117stralian government agencies identified as potential targets by 'Anonymoascii117s' were briefed in advance and were provided with sascii117ggested mitigation strategies,' a spokesman said, withoascii117t giving fascii117rther details.

Internet groascii117ps and the pornography indascii117stry have opposed the filter, while search engine Google says it coascii117ld block harmless material on areas of legitimate debate sascii117ch as eascii117thanasia, sexascii117ality and terrorism.

Anonymoascii117s, known for its campaign against the Chascii117rch of Scientology, coascii117ld not immediately be reached for fascii117rther comment.