Hundreds of thousands of Muslims have gathered in Bangladesh for what is considered the faith's second largest congregation after the Hajj pilgrimage.
Many sermons will call for world peace, organisers say
The three-day Biswa Ijtema, or Islamic prayer meeting, is taking place in Tongi, just outside the Bangladeshi capital, Dhaka.
Organisers expect two million devotees from 65 countries by Sunday.
Islamic scholars are reciting and explaining verses from the Koran and delivering sermons.
The BBC's Waliur Rahman in Dhaka says discussions on politics are banned in the meeting and many sermons will call for world peace.
Scholars and theologians will show how the holy book of Islam shuns violence, organisers say.
Two million devotees from 65 countries are expected by Sunday
The sermons are being delivered in several languages, including Arabic, Bengali and Urdu.
Police said security had been increased in the area of makeshift tents constructed from jute sacks that cover 160 acres on the banks of the river Turag.
Thousands of uniformed and plain-clothed security personnel as well as sniffer dogs have been deployed in and around the venue.
Mohammad Rowshan Monir, of the event's organising committee, said: "So far the event has run smoothly but it is a massive logistical exercise."
One Bangladeshi devotee, Golam Motin Talukder, 55, told the AFP news agency: "I came here to be righteous and to gain salvation. It is important because here we can be united with other Muslims in solidarity and equality."
Another, Mohammed Nurujjaman, 22, said: "I came here to reform myself so I can be a proper Muslim."
On Sunday, a mass prayer meeting will be held, attended by Bangladeshi Prime Minister Begum Khaleda Zia, President Iajuddin Ahmed and the leader of the main opposition Awami League, Sheikh Hasina Wajed.
Only the annual Hajj pilgrimage to Mecca in Saudi Arabia is thought to attract more Muslims.