Organised by the Tablighi Jamaat, "Biswa Ijtema" or the world congregation of Muslims started with a religious sermon by Indian scholar Maulana Ismail Hossain Batla.
The first phase of the gathering, being held on the banks of the river Turag amid tight security, will end on January 26. The second phase will start on January 31 and will continue till February 2.
The Biswa Ijtema has been held each year since 1967 to revive the tenets of Islam and promote global peace.
Earlier in the day, three people died at the Ijtema venue. The reason for the death of two devotees could not immediately be ascertained while one person died of diarrhea, a doctor told the Daily Star newspaper.
Meanwhile, authorities said they would organise a mass wedding without dowry at the Ijtema ground.