A group that says it targets online activity linked to so-called Islamic State (IS) has claimed it was behind an attack on the BBC's website.

All the BBC's websites were unavailable for several hours on New Year's Eve after what a BBC source described as a "distributed denial of service" attack.

The group, calling itself New World Hacking, said it had carried out the attack as a "test of its capabilities".

The BBC has not confirmed or denied such an attack caused the problems.

The corporation's press office said on Saturday that the BBC would not be commenting on the group's claim.

A "distributed denial of service" attack, which the group claims it carried out, aims to knock a site offline by swamping it with more traffic than it can handle.

In a tweet to BBC technology correspondent Rory Cellan-Jones, the group said: "We are based in the US, but we strive to take down Isis [IS] affiliated websites, also Isis members.