The family of a Nigerian Islamic studies lecturer accused of being a Boko Haram leader has told the BBC that his arrest was a "set up".
They said it was outrageous to suggest he belonged to the militants behind the insurgency in northern Nigeria.
Muhammad Nazeef Yunus was paraded before journalists this week, accused of recruiting militants in the central Kogi state where he lectures.
"In his research thesis, he condemned Boko Haram," his brother told the BBC.
Boko Haram's insurgency, which began in earnest in 2010, has centred in the largely Muslim north-east of Nigeria, where three states have been under emergency rule since May as the security forces try to crush the militants.
The group, which is opposed to Western education, wants to impose strict Islamic law in northern Nigeria.
Mr Nazeef, who is an assistant lecturer in Arabic and Islamic Studies at Kogi State University, was paraded along with four other suspects accused by the secret police of plotting to launch attacks in Igalaland, Kogi state.
The BBC's Ishaq Khalid in Jos, the capital of Plateau state where the lecturer and his family live, says Mr Nazeef was arrested on 29 October, a few days after publicly criticising the Nigerian authorities.
In a sermon at a mosque in Jos he had said the way heads of security agencies were appointed was a concern, suggesting they were biased against Muslims, our reporter says.
"Certainly, this is a set up," the lecturer's wife, Sa'adatu Shu'aibu, told the BBC Hausa Service about the arrest.
"[Everybody] knows that Nazeef Yunus is not a member of Boko Haram. People are witnesses to his preaching and I also listen to recordings of the preaching and I never heard him preach violence," she said.
His brother, Hadi Yunus, agreed that Mr Nazeef, who is also the director of a secondary school in Jos which follows an Islamic and Western curriculum, often lectured against the ideologies of Boko Haram.
One of the suspects arrested along with Mr Nazeef said he was recruited in May after he lost his job and was paid ($315, £195) a month by the group.
Along with the other young men paraded before journalists in the capital, Abuja, he alleged that he had been indoctrinated by Mr Nazeef, the alleged leader of the cell in Kogi state.
"I was shocked when the other suspects insisted that I was a member and the one that recruited them into the sect. I have never been a member of Boko Haram for one minute in my life, I even preach against them," he said.
Boko Haram, which along with its offshoot Ansaru, was last week blacklisted as a terrorist organisation by the US.
On Wednesday, MPs in Nigeria's lower house of parliament unanimously backed extending the state of emergency in the north-east for a further six months following a closed-door briefing by security chiefs.
The upper house had already given its consent after President Goodluck Jonathan's extension request earlier this month.