The protesters had gathered to hear their neighbours denounced as heretics and infidels.
Ahmadiyyas must be declared non-Muslim, protesters say
"Kaffir, kaffir," the mullah shouted into his microphone again and again, looking over the crowd from the makeshift stage set up on the back of a truck. "Infidel, infidel."
And he led the demonstrators in a chant: "Ahmadiyyas are not Muslims."
For four hours, the leaders of the International Khatme Nabuwat Andolon exhorted their followers in the main square of Bangladesh's northern town of Bogra.
The crowd swelled to far more than 5,000, most wearing skull caps.
At times the voices of the speakers cracked with emotion and they sobbed into the microphone.
There were tears among their audience too, and shouts of rage.
The target of this passionate hatred was the Ahmadiyya community, sometimes called Ahmadis.
"They don't obey our prophet as the last prophet," shouted one supporter.
"We'll force the government to ban them," added the protester next to him.
Another vowed: "We'll continue our jihad against them, we'll continue our marches."
There are 100,000 members of the Ahmadiyya community in Bangladesh.
They are scattered in pockets in cities, towns and villages up and down the country.
The campaigners of the International Khatme Nabuwat Andolon Bangladesh has organised a series of rallies demanding that the government formally declare that members of the sect are not Muslims.
In Bogra, the protesters had threatened to lay siege to the Ahmadiyya mosque.
For the members of the community in the town it was a day of real fear.
Inside their compound, behind police barricades, they were sitting in their tiny prayer hall.
Just a few dozen pairs of sandals were lined up outside.
In Bogra, as throughout Bangladesh, the Ahmadiyyas are a tiny minority.
They were having a lesson in their religion, sitting on the floor, listening to a teacher.
The sect was founded by Hadhrat Mirza Ghulam, who was born in the town of Qadian in Punjab in 1835.
The Ahmadiyyas believe he was the Imam Mahdi, or the Promised Messiah.
The more orthodox are still waiting for his arrival.
It is a doctrine that has led to their movement being persecuted in some countries.
In Pakistan, legislation was passed in 1974 declaring the Ahmadiyya community non-Muslims after a series of riots.
But until recently they were allowed to worship without interference in traditionally tolerant Bangladesh.
"We did not think that we would have to face such a situation because we believe in Allah and we pray for Allah," says Khandker Azmal Haq, the president of Rajshahi Ahmadiyya Muslim Jamaat.
The capital, Dhaka, has also seen big rallies against the Ahmadiyya
"So in this praying house, why do these people come to crush us?"
Already the government has bowed to some of the protesters' demands.
In January 2004, the home ministry issued a notice announcing that books published by the Ahmadiyya community were outlawed.
A statement said the ban "was imposed in view of objectionable materials in such publications that hurt or might hurt the sentiments of the majority Muslim population of Bangladesh".
Human rights lawyers are challenging the ruling in the courts.
They believe an important principle is at stake.
"There is a tendency to establish a monolithic, mono-religious strain in the political situation in Bangladesh," says Sultana Kamal, a lawyer with the human rights organisation Ain o Salish Kendra.
"We think this is just one of the cases, that there will be very many cases if this is not stopped right now."
In the end the protesters were kept away from the Ahmadiyya mosque in Bogra.
But later in the evening, after they had dispersed, the police replaced the signboard on the building.
It read: "The Qadiani upasanalaya (place of worship) in Bogra town: Muslims, do not be fooled into thinking it is a mosque."
Watching, some members of the Ahmadiyya community burst into tears.
It was a small concession by the local police to the demands of the International Khatme Nabuwat Andolon, but the campaigners want much more.
They have given the government until 23 December to declare the Ahmadiyyas are not Muslims, otherwise, said one speaker in Bogra, there will be blood in the streets.