Thousands of Shiite Muslims from Afghanistan and Pakistan are being recruited by Iran to fight with President Bashar al-Assad's forces in Syria, lured by promises of housing, a monthly salary of up to $600 and the possibility of employment in Iran when they return, say counterterrorism officials and analysts.
These fighters, who have received public praise from Iran's supreme leader Ayatollah Ali Khamenei, even have their own brigades, but counterterrorism officials in both countries worry about the mayhem they might cause when they return home to countries already wrestling with a major militant problem.
Amir Toumaj, Iran research analyst at the U.S.-based Foundation for the Defense of Democracies, said the number of fighters is fluid but as many as 6,000 Afghans are fighting for Assad, while the number of Pakistanis, who fight under the banner of the Zainabayoun Brigade, is in the hundreds.
In Afghanistan, stepped-up attacks on minority Shiites claimed by the upstart Islamic State group affiliate known as Islamic State in the Khorasan Province could be payback against Afghan Shiites in Syria fighting under the banner of the Fatimayoun Brigade, Toumaj said. Khorasan is an ancient name for an area that included parts of Iran, Afghanistan, Pakistan and Central Asia.
"People were expecting blowback," said Toumaj. IS "itself has its own strategy to inflame sectarian strife."
Shiites in Afghanistan are frightened. Worshippers at a recent Friday prayer service said Shiite mosques in the Afghan capital, including the largest, Ibrahim Khalil mosque, were barely a third full. Previously on Fridays — the Islamic holy day — the faithful were so many that the overflow often spilled out on the street outside the mosque.
Mohammed Naim, a Shiite restaurant owner in Kabul issued a plea to Iran: "Please don't send the poor Afghan Shia refugees to fight in Syria because then Daesh attacks directly on Shias," he said, using an Arabic acronym for the Islamic State group.
Pakistan has also been targeted by the IS in Khorasan province. IS has claimed several brutal attacks on the country's Shiite community, sending suicide bombers to shrines they frequent, killing scores of devotees.
In Pakistan, sectarian rivalries routinely erupt in violence. The usual targets are the country's minority Shiites, making them willing recruits, said Toumaj. The most fertile recruitment ground for Iran has been Parachinar, the regional capital of the Khurram tribal region, that borders Afghanistan, he said. There, Shiites have been targeted by suicide bombings carried out by Sunni militants, who revile Shiites as heretics.
In June, two suicide bombings in rapid succession killed nearly 70 people prompting nationwide demonstrations, with protesters carrying banners shouting: "Stop the genocide of Shiites."
A Pakistani intelligence official, who spoke on condition of anonymity because he is not authorized to speak to the media, said recruits are also coming from northern Gilgit and Baltistan. Recruiters are often Shiite clerics with ties to Iran, some of whom have studied in seminaries in Iran's Qom and Mashhad cities, said a second Pakistani official, who also spoke on condition he not be identified because he still operates in the area and exposing his identity would endanger him.
Yet fighters sign up for many reasons.
Some are inspired to go to Syria to protect sites considered holy to Shiite Muslims, like the shrine honoring Sayyida Zainab, the granddaughter of Islam's Prophet Muhammed. Located in the Syrian capital of Damascus, the shrine was attacked by Syrian rebels in 2013. Others sign up for the monthly stipend and the promise of a house. For those recruited from among the more than 1 million Afghan refugees still living in Iran it's often the promise of permanent residence in Iran. For Shiites in Pakistan's Parachinar it is outrage at the relentless attacks by Sunni militants that drives them to sign up for battle in Syria, said Toumaj.
Mir Hussain Naseri, a member of Afghanistan's Shiite clerics' council, said Shiites are obligated to protect religious shrines in both Iraq and Syria.
"Afghans are going to Syria to protect the holy places against attacks by Daesh," he said. "Daesh is the enemy of Shias."
Ehsan Ghani, chief of Pakistan's Counterterrorism Authority, told The Associated Press that his organization is sifting through hundreds of documents, including immigration files, to put a figure on the numbers of Pakistanis fighting on both sides of the many Middle East conflicts, including Syria. But it's a cumbersome process.
"We know people are going from here to fight but we have to know who is going as a pilgrim (to shrines in Syria and Iraq) and who is going to join the fight," he said.
Pakistan's many intelligence agencies as well as the provincial governments are involved in the search, said Ghani, explaining that Pakistan wants numbers in order to devise a policy to deal with them when they return home. Until now, Pakistan has denied the presence of the Islamic State group in Pakistan.
Alireza Nader, a senior policy analyst at the U.S.-based RAND Corp., said Afghan and Pakistani recruits also provide Iran with future armies that Tehran can employ to enhance its influence in the region and as protection against perceived enemies.
Despite allegations that Iran is aiding the Taliban in Afghanistan, Nader says battle-hardened Shiite fighters are Tehran's weapon should relations with an Afghan government that includes the radical majority Sunni religious movement deteriorate.
"Once the Syrian civil war dies down Iran is going to have thousands, if not tens of thousands of militia, under its control to use in other conflicts," he said. "There is a potential of Iran getting more involved in Afghanistan using militia because Iran is going to be really concerned about security on its border and it would make sense to use a proxy force."
Pakistan too has an uneasy relationship with Iran. On occasion the anti-Iranian Jandullah militant group has launched attacks against Iranian border guards from Baluchistan province. In June, Pakistan shot down an Iranian drone deep inside its territory.
In Pakistan the worry is that returning fighters, including those who had fought on the side of IS, could start another round of sectarian bloodletting, said the intelligence official.
Associated Press writers Amir Shah in Kabul, Afghanistan; Munir Ahmed in Islamabad, Pakistan; Riaz Khan in Peshawar, Pakistan and Nasser Karimi in Tehran, Iran, contributed to this report.