They said they were astonished to see so many pilgrims on the way to Karbala, central Iraq.
'Imam Hussein (AS) movement has become universal and the enemies of Islam are extremely afraid of people's unity,' the pilgrims said, 'Many US Muslims wish they could join the Arbaeen procession.'
It is estimated that 20 million people will attend the religious ceremony in different cities of Iraq.
According to statistics, two million 400 thousand visas have been issued for Iranians. About one million 700 thousand have entered Iraq so far.
Arbaeen, an Arabic word meaning the 40th, is a mourning ceremony held 40 days after Imam Hussein, Prophet Muhammad's grandson, and his 72 followers, including 18 of family members and close relatives, were brutally martyred in Karbala on Ashura, the 10th day of the Arabic year, by the army of the second Umayyad caliph, Yazid, in AD 680.
The mourning ceremony began and was soon established when Jabir ibn Abdollah Ansari, a close follower of Prophet Mohammad (PBUH), then 77, visited Imam Hussein's grave as the Imam's first pilgrim, 40 days after Ashura.