The threat of a formidable Islamic State grows, as the Pakistani Taliban pledged support to the fearsome terrorist group and urged other Middle Eastern extremists to be part of the effort to repel the alleged Western campaign against Islam.

As the Muslim world celebrated the holy festival of Eid al-Adha, the Pakistani branch of the Taliban (TTP) has expressed their support for the Islamic State (IS, formerly ISIS) in an email to Reuters, sent from an unknown location.

"Oh our brothers, we are proud of you in your victories. We are with you in your happiness and your sorrow," read the emotional message from their spokesman.

"In these troubled days, we call for your patience and stability, especially now that all your enemies are united against you. Please put all your rivalries behind you…

"All Muslims in the world have great expectations of you ... We are with you, we will provide you with Mujahideen [fighters] and with every possible support,” the confession reads.

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It was released in Arabic, as well as Urdu and Pashto and came shortly after the IS’s latest execution, that of a British humanitarian worker, beheaded on video on Friday.

The message was followed by another show of support from a splinter group within the Pakistani branch. It expressed a wish to mediate between the rivaling IS and the Syria-based Al-Nusra Front – a group taking its roots from Al Qaeda, whose relationship with the IS has faced a few bumps lately, owing to a difference in ambitions.

Proof that the worrisome Taliban-IS alliance is for good is scarce at this time, but IS activists in Pakistan have been seen distributing pamphlets praising the group on the streets of Peshawar recently. The same mood could be seen in India, as IS flags could be spotted at street rallies in the Indian-administered Kashmir.

None of these are a good sign for global powers, whose main fear of late has been the rapid expansion of IS ranks to include other terrorist groups and a growing number of civilians joining its cause.

Also, while the Pakistani leadership wants to set up a Sharia state there, the IS has shown no interest in South Asia. And the Taliban itself has seen emerging divides in the past year, one of its factions splintering off due to a disagreement over the 2013 appointment of the new leader, Mullah Fazlullah.

The same hasn’t yet been said for the structure of the IS, which seems to just grow and accumulate followers and fighters, as well as Western businessmen, logisticians and IT specialists who’ve become radicalized.

If the decision by Pakistan’s primary militant faction to offer material and arms support to the IS is set in stone, the regional consequences could be enormous, especially after US withdrawal from Afghanistan, which practically every analyst out there said would lead to a dangerous power vacuum that emerging terrorist groups would be happy to fill, the way they did in Iraq, Libya and Syria.

And yet, this could be just what the IS is looking for: a huge Muslim region fiercely opposed to the West, and containing hundreds of thousands of youths, former fighters and disenchanted people looking to unite for a cause.