ISIS terrorists have increase its Propaganda about launching terror attacks on UK soil.

Last month, Abdullah Elmir – dubbed the Ginger Jihadi because of his long red hair – bragged to an undercover Mail on Sunday reporter that ISIS would not stop their murderous campaign until its flag was flying over Buckingham Palace.

It followed the online circulation of a series of terror manuals providing step-by-step instructions on how to launch 'lone wolf' attacks in the UK, Mail online reports.

Compiled by an extremist who claimed to be from England, the document carried the strapline: 'A guide to strike terror in the hearts of the kuffar [non-believers] of the West.'

Police launched an urgent investigation after Elmir, 18, who fled his home in Australia last year and later turned up in Syria, sent a horrific warning to this newspaper that supporters of the terror group are planning attacks in London.

Elmir said we are itching to do an attack.' He added: 'This is a direct threat.'

Meanwhile, a British man who claimed to be fighting alongside terrorist in Syria boasted in a BBC Radio 5 Live interview broadcast last year: 'If and when I come back to Britain it will be when this khilafah – this "Islamic state" – comes to conquer Britain and I come to raise the black "flag of Islam" over Downing Street, over Buckingham Palace, over Tower Bridge and over Big Ben.'