The first phase of Biswa Ijtema, the second largest congregation of Muslims after Hajj, began on the banks of the Turag River in Tongi after Fazr prayers on Friday.
The Ijtema began with "a'm bayan" (general sermons) by Pakistani Islamic scholar Maulana Obaidul Khorshed.
Several thousand devotees are expected to offer Jum'a prayers on the first day of the Ijtema.
Thousands of devotees from home and abroad started thronging on the bank of the Turag River to take part in the religious event to seek divine blessings of the Almighty Allah.
The three-day of the 55th Biswa Ijtema will end on January 12. The followers of Maulana Jubair Hassan will participate in the first phase of Biswa Ijtema.
Additional police have been deployed in and around the Ijtema venue to ensure security of the devotees. The venue has been brought under CCTV surveillance.
Tabligh Jamaat has been organising the congregation at the venue since 1967. In 2011, Tabligh split the Ijtema into two phases, dividing the participation of the people of 64 districts, to reduce pressure on the venue and ensure better management.