A malicious hacking attack on a Christian dating site has been used to break into Facebook accounts and post obscene and racist comments.

The online group called 4chan - which hacked former Alaskan governor Sarah Palin's email account and spread hoax news about a spate of celebrity deaths - is now targeting Christians on Facebook.

Hackers defaced a Facebook page that was asking people to pray for a sick relative by posting the message “If he dies can I have some of his stuff?”.

The hackers stole login details and passwords from an unnamed Christian dating site and used them to break into Facebook accounts.

In one instance, they superimposed a target's face on to a picture of a naked woman and published it on her Facebook page, pretending they had uploaded the wrong picture by mistake.