ISLAMABAD (AFP) - The Islamic State in Iraq and Syria (ISIS) is starting to attract the attention of radicals in Pakistan and Afghanistan, long a cradle for Islamist militancy, unnerving authorities who fear a potential violent contagion.

Far from the militants' self-proclaimed "caliphate" in Iraq and Syria, the name of ISIS has cropped up several times in jihadi circles in recent weeks in Pakistan and Afghanistan, the historic homeland of the Taleban and Al-Qaeda.

Leaflets calling for support for ISIS were seen in parts of north-west Pakistan, and at least five Pakistani Taleban commanders and three lesser cadres from the Afghan Taleban have pledged their support.

Pro-ISIS slogans have appeared on walls in several cities in both countries and in Kabul University, where a number of students were arrested. Militant, security and official sources questioned by AFP in recent weeks say these are local, individual initiatives, and at this stage ISIS has not established a presence in the region. But the success of ISIS in the Middle East is unsettling many of those charged with keeping a lid on Afghanistan and Pakistan's myriad extremist groups.

"ISIS is becoming the major inspiration force for both violent and non-violent religious groups in the region," Pakistani security analyst Amir Rana told AFP.

- Warning letter -

Earlier this month, Pakistan's National Counter Terrorism Agency wrote to a dozen government agencies warning them to be on their guard against the ISIS group.

"The successes of ISIS play a very dangerous, inspirational role in Pakistan, where more than 200 organisations are operational," the agency said.

The letter came as the Pakistani army fights a major offensive in insurgent bastions of the tribal north-west, which appears to be weakening its major enemies, the Tehreek-e-Taleban Pakistan (TTP) and allied Al-Qaeda fighters.

Following the army offensive, the TTP, a coalition of disparate militant groups, has fragmented into rival factions over recent weeks, fuelling rumours that the movement could be overtaken by ISIS.

The TTP say they broadly support both the ISIS militants and Al-Qaeda. They also say say they have sent 1,000 fighters in recent years to help the militant struggle in Syria - an estimate confirmed by a Pakistani government source - and plan to send 700 more.

But if ISIS militants one day envisage extending their influence in Afghanistan and Pakistan, the world's only Islamic state with nuclear weapons, they will have to either defy or find an accommodation with the two countries' Taleban movements.

Currently both the TTP and the Afghan Taleban officially recognise only one leader, Mullah Omar, and a senior Afghan cadre told AFP that ISIS was wrong to declare a caliphate.

"The Taleban and their supporters say that 'amir-ul-momineen' (the commander of the faithful) has already been chosen," the commander told AFP, rejecting ISIS leader Abu Bakr al-Baghdadi.

- Money, money, money -

So far, the Taleban and Al-Qaeda's new South Asia wing have steered clear of criticising ISIS, maintaining a united front against "Western aggression".

US officials say the group is generating tens of millions of dollars a month from black market oil sales, ransoms and extortion. This financial heft is proving a big draw - including for the five Pakistani Taleban commanders who announced their support for the ISIS.

"The splinter groups are facing financial crisis, so they are contacting Daesh," a senior militant told AFP. Daesh is another name for ISIS.

To spread in the region, ISIS must also eat away at the authority of the state - but, unlike Iraq and Syria, Pakistani state structures look solid and are supported by a powerful army.

Afghanistan, much more fragile, is more worrying - particularly Kunar and Nuristan, mountainous provinces on the Pakistani border, which have long been refuges for militants from the hardline branch of Islam espoused by ISIS and Al-Qaeda.

"The authorities' fear is that IS will join up with the TTP and other extremist groups and from there spread on both sides of the border," said analyst Rana.

Several sources say that in Kunar there is at least one camp training hundreds of fighters sympathetic to ISIS.

Away from the camps, there is a danger that the ISIS militants could attract more and more young Afghans and Pakistanis through their propaganda on Facebook and Twitter.

"People here face problems with the lack of justice, the corruption and the inefficiency of the state, and therefore they need a counter-narrative, and ISIS provides one with religious content," said Tahirul Ashrafi, head of the Pakistan's Ulema Council, seen as close to the authorities.

In the short-term, the big fear in Pakistan stems from the ISIS group's sectarian agenda, more extreme and more explicit than that of Al-Qaeda, heightened by its fight against majority Shiite governments in Iraq and Syria.

Violence against minority Shiite Muslims, who make up about 20 per cent of Pakistan's population, has hit record levels in recent years and there are concerns ISIS could energise sectarian groups even further.