Australian atheists are under attack, with the websites of both the Atheist Foundation of Australia and the Global Atheist Convention knocked offline in a major cyber attack yesterday afternoon.

The "distributed denial of service" attacks flooded the websites with traffic, forcing them offline about 5.20pm yesterday.

Author Richard Dawkins, who wrote The God Delusion, lends his support as the London bus atheism advertising campaign is launched. Credit:Reuters

As of this morning, the foundation had still not been able to restore the websites.

The attacks may be related to the Global Atheist Convention, which is being held in Melbourne in March next year. Speakers include Richard Dawkins, author of The God Delusion and comedy writer Catherine Deveny.