Extremist group ISIS (Islamic State of Iraq and al-Sham) has reportedly issued Islamic State passports to give an air of legitimacy the unrecognised area of the Middle East under their control.

Photos of the passports showed its exterior cover is black, based on the jihadist flag, with the inscription "State of the Islamic Caliphate" on the cover. The document likewise also had a statement that allegedly says, "If the holder of the passport is harmed we will deploy armies for his service."

Printed in a government printing facility in Mosul, the new document will be distributed to 11,000 citizens living in cities bordering Iraq and Syria.

But global experts downplayed the image of the ISIS passport that has been rounding the social media. Apart from just being a symbolic gesture, analysts said they were just mere tools used by the terror group to saw psychological warfare among the other global nations.

Read: ISIS Recruits Children, Brainwashes Them to Kill Christians; Vatican Says Military action 'Probably Necessary'

"Illusions of a Caliphate. ISIS issue passports as part of psychological warfare," Dr Magnus Ranstorp, a Swedish academic who briefs senior government and security officials on the threat of Islamic terrorism, said as he tweeted the photograph.

"ISIS now issuing passports, I'm sure they won't create panic and alarm at airport check in desks," Ghaffar Hussain, managing director of the world's first counter-extremism think tank Quilliam, said.

Meantime, leaflets promoting the terror group have been reportedly being distributed in London's busiest tourist districts, Oxford Street, on Tuesday.

One side of the flyer reads, "After many attempts and great sacrifices from the Ummah of Islam throughout the world, the Muslims with the help of Allah have announced the re-establishment of the Khilafah and appointed an Imam as Khaleef."

The other side goes, "Congratulations and Glad Tidings."

This pro-ISIS leaflet was being handed out in Oxford Street in London today, worrying times - pic.twitter.com/Ala9rP2Zk9

— Ghaffar Hussain (@GhaffarH) August 12, 2014

This pro-ISIS leaflet is being handed out by students in London @WashingtonPoint pic.twitter.com/l7W34nuoE8

— Mete Sohtaoğlu (@metesohtaoglu) August 12, 2014

All these people are not muslims, so I'm told RT@GhaffarH ISIS supporters handing out ISIS propaganda in London - pic.twitter.com/2N0j3EBHFn

— Arnoud Veilbrief (@ArnoudVbrief) August 12, 2014

Investigations are underway as to who organized the distribution.

"They were being handed out by a group of individuals from Luton. They were doing it quite brazenly," the Financial Times quoted Ghaffar Hussain, managing director of the Quilliam Foundation, a UK anti-extremism think-tank.

"To have such a group openly promoting Isis - a terror organisation known for its brutality - in London, in one of its busiest areas, is shocking."

YouTube/RT