Thousands of Iranians are crossing the poorly-policed border with Iraq to make the pilgrimage to the Shia shrine cities of Kerbala and Najaf. Many of them are crossing with the apparent nod of low-level officials on both sides, despite fears that foreign agents are leaking into Iraq to foment violent unrest.
The border crossing itself can be dangerous, and pilgrims' stories carry the stamp of human courage. Braving minefields, bandits and border guards, they walk for hours or even days with no shelter across a barren and sun-baked no-man's land, strewn with military wreckage from the Iran-Iraq war.
Hussain, aged 16, said: "We were set down by the bus and then walked for 10 hours across the desert at night. It was very dry and we only had water for three hours. When we stopped for a rest, I was so tired I fell asleep standing up and dropped to the ground."
At the end of the walk, minivans were waiting to carry Hussain and his family to Kerbala. They were among the lucky ones. The Iranian press reported last month that nearly 300 people had died trying to reach Iraq since the fall of Saddam Hussein. The New York Times has reported that more than 17,000 Iranians have been turned back by US forces.
Shias regard the pilgrimage to Kerbala and Najaf as a permissible alternative to the haj, the pilgrimage to Mecca demanded of all Muslims who can afford the journey. In Saddam's time, the trip was expensive and Shias complained of harassment at the shrines. Now they can worship freely and are coming in droves.
Iranian currency has become commonly accepted by Iraqi shopkeepers and hoteliers, according to pilgrims who recently returned to Iran. The pilgrims saw large numbers of other Iranians at the shrines of Ali and Hussain, the first and third Shia Imams.
Their numbers are swelled by Iraqis resident in Iran who want to visit relatives, and by Iranians whose families have lived in Iraq's shrine cities for generations. The reunions, often after more than 20 years of enforced separation, are incredibly moving.
"We had travelled for more than 24 hours, but when I arrived at my uncle's house in Kerbala, I was so happy I could not sleep," said Leila Vakili, 21, an English student from a distinguished Iranian religious family that has lived in Kerbala for three generations.
"One of the men on our bus had left Iraq at the age of 10 when the war began with Iran. His parents had been killed but he knew his brother and sister were still alive. When we dropped him off, we could hear the screams of joy from inside the house as the bus pulled away. After that, everybody was even more anxious about finding their own relatives safely," she said.
In a working-class district of south Tehran, I met a goldsmith who acts as middleman for those wanting to make the trip. He organises guides across the Kurdish mountains, and minivans to transport people on either side of the border. He says there are fewer security patrols there. Many pilgrims avoid crossing in Kurdistan, where Iranians fear betrayal by their guides or attacks by mountain bandits.
"Our guides show you where to crawl through the searchlights and guide you round the minefields and across the mountains to where a bus is waiting," he says. For all its dangers, the trip costs the equivalent of £70 affordable to Iran's poor but devoutly religious uneducated classes.
For those with family or political connections, there is a safer route right through the border checkpoints. Although things have tightened since the assassination in September of Ayatollah Bakr al-Hakim, pilgrims say they know people who have succeeded in bribing border guards or posing as Iraqi refugees trying to return home. Forged Iraqi identity cards can be bought for $3 (£1.78) in Marveh Alley, the Arab quarter of Tehran.Reuse content