KARBALA, Iraqinfo-icon (AP) -- Millions of Muslims from around the worldinfo-icon are making their way this week to the holy shrines of Karbala in southern Iraq, a pilgrimage that is as much about community as it is about religioninfo-icon.

The shrines are of two revered Islamic figures Imam Hussain, the grandson of the Prophet Muhammad (Pbuh), and his half-brother and standard bearer Abul Fazal Abbas. The annual commemoration, called Arbaeen, draws more pilgrims each year than the hajjinfo-icon in Saudi Arabiainfo-icon, a pilgrimage required once in a lifetime of every Musliminfo-icon who can afford it and is physically able to make it.

Pilgrims stream toward Karbala on foot from the cities of Najaf, 80 kilometers away, Baghdadinfo-icon, 90 kilometres to the north, and other places farther afield, resting along the way in tents lined with foam mattresses and fleece blankets.

"Our fathers and our grandfathers walked to Karbala, and God willing, our children will, too," said Karrad Karim, a 24-year-old pilgrim journeying with four friends from Baghdad. They brought with them large flags bearing devotional sayings to the Shiainfo-icon imams but little in the way of supplies for the four-day journey.

That's because along the roads, stalls set up by charities, mosques, and volunteer groups see to it that no traveler goes hungry. Cooks prepare vast amounts of stewed lamb, grilled fish, fresh bread, and rice for the pilgrims, refusing payment for the meals.

The pilgrimage, known in Arabic as the Ziara, marks the 40th day of mourning of the anniversary of the brutal massacre of Imam Hussain and his small band of family and followers by the 7th century Umayyad tyrant Yazeed, during the tumultuous first century of Islam's historyinfo-icon.

Imam Hussain was seen by his followers as the rightful heir of the prophet's legacy. When he refused to pledge allegiance to the Umayyad caliphate, he was slain, cementing the schism between Muslims. Imam Hussein's half-brother Abbas was also slain when he reached the banks of Euphrates in the burning desert while trying to fetch water for the hungry and thirsty caravan which included small children.

Modern depictions of Imam Hussain, stitched on banners displayed along the pilgrimage, show him with blood on his brow and bearing a Christ-like countenance.

But the mood is not all somber among the pilgrims. Spirits were high as travelers approached Karbala, and improved further with generous helpings of datesinfo-icon and tea.

"This is a walk to heaven," said Alaa Dadi, 45, who was making his way with his wife and three children.

Sunnis outnumber Shias by a wide margin among the world's estimated 1.5 billion Muslims, and Shia rituals are far less known. The hajj is considered one of the five pillars of Islam, and an obligation for all Muslims -- Sunni and Shia. The Ziara is voluntary and holds little significance in Sunni tradition.

In recent years, the Iraqi government says Karbala received 10-20 million visitors during the event, with many Shia pilgrims, earlier banned from visiting holy shrines by the fallen dictator Saddam Hussein and his predecessors, coming from all across Iraq. No figures have yet been released for 2018.

This year's pilgrimage is the first since Iraq's government declared victory over the Daesh Islamic Stateinfo-icon group in January, but the threat of insurgent attacks still lingers. The terror group has deliberately targeted Pilgrims enroute Karbala in the past to sow fear but of no avail. 

Iranian religious affairs official Hussein Zulfighari said 1.7 million Iranians had already crossed into Iraq for the pilgrimage, and predicted the number could reach 2 million by the event's climax on Tuesday. Zulfighari, quoted in Iraninfo-icon's Fars newsinfo-icon agency, said the visitors include 50,000 Afghan's living in Iran.

Muhammad Thiqawi, 57, from Iran, said he was initially hesitant about making the journey this year. A month ago, protesters in Iraq's southern city of Basrainfo-icon burned down Iran's Consulate over what they felt was the country's undue influence over Iraqi affairs. Iran, the region's Shia power, exerts considerable sway over Iraqi politics.

But, he said, "the Iraqis hosted usinfo-icon in their homes and welcomed us. They said Iranians are our friends and guests of (imam) Hussain." On his child's stroller, he pinned a poster of the two countries' flags.

Ali al-Alizi, 35, traveled from Qatif, a Shia province in eastern Saudi Arabia that has been the target of repression by the ruling regime.

Lord Maurice Glasman, a Labour peer in Britaininfo-icon's House of Lords who was raised Jewish, said he came at the encouragement of his Iraqi friends to better understand the country that defeated the Islamic State group's insurgency.

"Politically, ethically, spiritually, it has been an extremely elevated visit," said Glasman, who arrived in Karbala on Sunday, after walking several days from Najaf.

The hajj saw 2.4 million pilgrims this year but Saudi authorities regulate the tradition tightly, driving up costs for pilgrims and depriving it of some of the spontaneity seen in the Ziara. For many Muslims who cannot afford to go on the hajj or cannot get the Saudi visa, the Ziara is a satisfying alternative.

"The hajj is required by God, but the Ziara is voluntary," said Sayyid Abdelamir Mousawi, 46. "Those who go do it out of love."