The first phase of a three-day Biswa Ijtema began on Friday on the bank of the Turag River at Tongi on the outskirts of the capital amid tight security, reports news agency UNB.
The Ijtema began with the deliberation of 'Aam Bayan' (general sermons) by noted scholar Maulana Obaidul Khorshed after Fazr prayers.
The 3-day Ijtema will end with Akheri Munajat (final prayers) on Sunday.
Several thousands of devotees from home and abroad started congregating to the Turag bank to take part in the religious event since Thursday.
The second phase of the Ijtema is scheduled to begin on January 20 at the same venue and end on January 22.
Tablig Jamaat has been organising the Ijtema at the venue since 1967. But, Ijtema is held in two phases since 2011 to ease the accommodation problem.
A five-tier security measure has been taken for the event along with deployment of several thousand members of different law-enforcement agencies, including Rab and police.
Rab members will patrol the ground and the adjacent areas with helicopters to monitor security measures.
Moulana Giasuddin, a senior member of the Ijtema organising committee, said devotees from 32 districts, 16 in each phase, will join the two phases of Ijtema this year.
Several health centres have been set up at different parts of the venue along with beds and almost all first aid and other treatment facilities with doctors doing round-the-clock duty at each centre.
Special measures have also been taken to ensure uninterrupted electricity supply during the three-day Ijtema.