Vast crowds of Muslims prayed near the Bangladeshi capital as the second largest annual Islamic congregation after the Hajj began Friday under tight security.
Over a million devotees flocked to the River Turag at Tongi, 40 kilometres (25 miles) north of Dhaka, as a scholar from Pakistan led the opening sermons of the Biswa Ijtema, or World Muslim Congregation.
The massive gathering, which also draws 25,000 foreign devotees from 130 countries, is being hosted after the South Asian country was plagued by election violence early this month.
At least 26 people were killed during the poll January 5, making it the bloodiest vote in Bangladesh's history, while hundreds of opposition supporters torched or trashed polling stations.
Scores of people were killed in clashes between police and opposition supporters including the Islamists in the lead-up to the elections from late October.
But officials said they had taken "foolproof" security measures with the deployment of 10,000 police and air and river patrols by the elite Rapid Action Battalion.
"We don't have any security threat, but we have taken enough security measures," police spokesman Shahidul Hoque said.
This is the third year the festival is being held in two phases to accommodate an ever-growing number of devotees, Nurul Islam, the district administrator who is also coordinator of the festival, told AFP.
TV stations broadcast images of pilgrims on both banks of the river, and on bridges, roads and rooftops around the venue, as the 165-acres (66.7 hectare) main prayer ground had already been filled to the brim.
"We estimate there are already more than one million devotees. People are now gathering in every open space," Islam said, adding the number of pilgrims would keep growing until final prayers on Sunday.
During the three-day congregation, Muslims pray and listen to religious scholars.
"We commit sins and mistakes in our daily lives, so I have come here to join the prayers with millions others to seek mercy from Almighty Allah," devotee Muhammad Ismail told AFP.
Tabligi Jamaat, a non-political organisation, which has tens of millions of followers across the globe, urges people to follow tenets of Islam in their daily lives. Both Tabligi members and non-members attend the festival.
The government has arranged trains and ferries to transport pilgrims while army engineers have set up dozens of makeshift bridges and water tanks to accommodate the huge crowd.
Bangladesh is the world's third-largest Muslim-majority nation, with Muslims making up nearly 90 percent of its 154 million population.
The second phase, which also lasts three days, will begin January 31.