Isis threat to blow up Big Ben and White House Reuters

Islamic State terror group has vowed to blow up world famous landmarks such as Big Ben, Eiffel Tower and the White House in a latest audio broadcast.

The chilling threat was made purportedly during an audio recording by the group's official spokesman Abu Muhammad al-Adnani.

"We will make you lives black and dark", he said.

British jihadist, Abu Abdullah Britani, 32, who fled the UK for Syria last year, has also taken to Twitter to repeat the chilling warning.

The Arabic broadcast, translated by the SITE Intelligence Group, comes as IS accepts Boko Haram's pledge of allegiance to expand its caliphate in West Africa, listing other cities "we want," from Paris and Rome to Jerusalem and Kabul.

"We announce to you to the good news of the expansion of the caliphate to West Africa because the caliph... has accepted the allegiance of our brothers of the Sunni group for preaching and the jihad," said al-Adnani yesterday, (12 March).

Anonymous hackers have since launched the OPISIS campaign to close down social media accounts of jihadists like Britani to stop them spreading extremist propaganda. But critics say it would be harder to trace and arrest the culprits.

"Closing down accounts is a bad idea, because this is how we monitor Isis members and gather intelligence," a spokesman for Global Vigilance, which targets Isis recruitment online, told the Mirror.

"The Anonymous OPISIS campaign is a double-edged sword."

On 13 March, more than 20,000 Iraqi troops and Shi'ite militias were taking part in the biggest offensive yet against IS by retaking the late Saddam Hussein's home city of Tikrit.

Adnani insisted that "the victories proclaimed by coalition are only illusions," and only "inches of land" had actually been recaptured.