Anonymous has declared war on Donald Trump over his hugely controversial proposal to ban Muslims from the US.

Supporters of the online group have posted a video online criticising the presidential hopeful’s comments. The group also appear to have briefly breaking the website for one of Mr Trump’s properties, the Trump Tower in New York.

In a video featuring a figure wearing the mask now associated with the group, supporters tell Mr Trump that by threatening to ban Muslims from the US he is playing into the hands of Isis.

"The more the United States appears to be targeting Muslims, not just radical Muslims, you can be sure that ISIS will be putting that on their social media campaign," the video says.

"Donald Trump, think twice before you speak anything. You have been warned," the video says.

Anonymous’s attacks on Mr Trump seems to be related to its “Operation Isis”. That has seen supporters seek out social media accounts and websites run by Isis supporters and attempt to take them down or have them removed.