Biswa Ijtema, one of the largest Muslim congregations in the world, began on the bank of the Turag River at Tongi here after Fazr prayers on Friday.
Ijtema began with "Aambayan" (general sermons) by Pakistani Islamic scholar Maulana Ziaul Haq.
This year, the Biswa Ijtema is being held for four days in a single phase.
On the first two days, followers of Maulana Jubair Hassan will participate in the Biswa Ijtema on Friday and Saturday and they will leave the ground after Akheri Munajat on Saturday afternoon.
Later, the followers of Maulana Muhammad Saad Al Kandhalvi will take part in the Biswa Ijtema on Sunday and Monday and conduct their Akheri Munajat on the last day.
Several lakh devotes are expected to offer Juma prayers on the first day of the Ijtema on Friday.
Thousands of devotees from home and abroad started thronging the bank of the Turag River to take part in the religious event to seek divine blessings of the Almighty Allah.
An eight-layer security measure has been taken for the event with the deployment of huge members of different law enforcement agencies in and around the Ijtema ground. The venue has been brought under CCTV surveillance.
There will be special train and bus services to ease the communication of the devotees.
Gazipur Metropolitan Police Commissioner YM Belalur Rahman on Thursday said the Ijtema ground is under CCTV surveillance and watchtowers have been set up to ensure security.
Members of law enforcement agencies are performing their duties while intelligence surveillance has been beefed up.
Check-posts have been set up in lanes, intersections and all the entries of the ground, said the GMP commissioner.
Besides, free medical camps have been set up near the Ijtema ground to provide free health care services and medicines among the devotees.
The first phase of Biswa Ijtem was scheduled to be held from January 11 to 13 while the second one from January 18 to 20 last, but those were postponed due to the December-30 national election.
Later, it was decided that the Biswa Ijteam would be held once instead of two phases this year.
Tabligh Jamaat has been organising the Ijtema at the venue since 1967.
The Ijtema was held in two phases from 2011 to 2017 to ease the accommodation and transportation problem.
