Najaf (IP)- Millions of pilgrims from different countries have gathered in the holy city of Najaf in Iraq, especially in the the Holy Shrine of First Shi'a Imam Hazrat Ali ibn Abi Talib (PBUH), to participate in the Arba'een Trek and start marching towards the holy city of Karbala and participate in the grand commemoration of Imam Hussein (PBUH).