Bangladesh's Biswa Ijtema, or World Muslim Congregation, is the world's second largest Islamic gathering after the Hajj with devotees coming from all over the globe to pray and hear imams preach for three days.
Canopies stretching for more than a kilometre, erected on open ground on the banks of the Turag river, were already packed with tens of thousands of worshippers even before the official start today, deserting the normally congested streets of the nearby capital Dhaka.
"Islam does not support killings. Even during the time of the Prophet, non-believers would satirise him and Islam, but he tolerated them and forgave them," said Mohammad Faiyaz, a senior Islamic scholar at the congregation.
Faiyaz said the "mindless and abominable killings" of journalists and police had tarnished the religion's image and made the work of preachers such as himself that much more difficult.
"These attackers simply don't know what Islam is all about," he told AFP.
Charlie Hebdo has a history of publishing cartoons mocking all religions, including Islam, and had been previously been firebombed after running caricatures of the Prophet Mohammed.
The gunmen were heard crying "we have avenged the Prophet" and "Allahu akbar" (God is greatest) after carrying out their killing spree.
But Zakaria said the idea that the Prophet's honour needed avenging by masked gunmen was absurd.
Launched by Tablig Jamaat, a non-political group that urges people to follow the tenets of Islam in their daily lives, the gathering at Tongi was first held in 1964 and now draws around three million people each January.
But Mohammad Arifuzzaman, a Tablig Jamaat follower, said the organisation would continue to send preachers to Europe to spread their message.
"I don't think this particular attack will deter us from preaching in Europe. We have been sending preachers to Europe for decades," said the 32-year-old from Dhaka.
"Our work did not suffer after other previous attacks where the carnage was bigger, such as the Twin Tower attacks" in New York on September 11, 2001, he said.
"We just invite people to do good work.
