Dhaka (CNN) Something deadly and frightening is happening in Bangladesh.

Gangs armed with machetes have been hunting down and killing liberal activists and outspoken critics of Islamist extremism.

The assassinations are occurring with alarming frequency. U.S. officials counted at least 35 attacks in 14 months in Bangladesh, U.S. Ambassador Marcia Bernicat said in an interview with CNN on Tuesday

Twenty-three of those attacks have been claimed by a terrorist group, she said.

Two fathers targeted for murder

Ananya Azad and Ahmed Reza Faruqi are two men who experienced this brutal violence first-hand.

Islamist militants carried out savage attacks against the fathers of both men.

Ideologically, the victims were polar opposites.

Azad's father, Humayun Azad, was a prominent atheist writer and poet. Militants slashed his face at a book fair in 2004. He was left horribly disfigured and passed away several months later.

Meanwhile, Faruqi's father, Sheikh Nur Islam Faruqi, was a well known Muslim cleric who preached peace and tolerance. In 2014, militants broke into his house, tied him up and slit his throat.

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Assassination of a Muslim cleric

Faruqi followed the Sufi interpretation of Islam, a belief steeped in mysticism, which preaches love amongst all and has deep roots in Bangladesh.

He also hosted a call-in television show about Islam. It was there that he often received threats from hardline Sunni Muslim fundamentalists who view Sufism as heresy.

"Many times they threatened my father over the phone (for) preaching Sufi Islam," the younger Faruqi said.

In the wake of his father's murder, Ahmed Reza Faruqi took over leadership of his father's mosque. He is also following in his father's footsteps by hosting television programs about Islam and spirituality.

Sufi cleric Ahmed Reza Faruqi has experienced brutal Islamist violence first hand in Bangladesh.

Faruqi spoke to CNN while seated barefoot on the stone floor of the Hazrat Shah Khwaza Sharfuddin Chisti Mazar Mosque, dressed in a white shalwar kamiz and wearing an embroidered golden cap.

He says he has a mission to continue spreading his father's message that Islam "is not the religion of terrorists."

"My father preached moderate Islam," Faruqi says.

"There are Christians, there are Hindus, there are Jews ... we respect them, we don't force them to obey our opinion."

But the bearded cleric worries about what he describes as the rising tide of extremism in his country.

"Bangladesh has to stop this (extremist) ideology," he says.

"If these (people) will not be stopped, there will be a massacre of people who love Sufism, who love moderate Islam."

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Son of an atheist

Ananya Azad embraces a diametrically opposed ideology, that of the so-called "free thinkers," an intellectual movement that espouses atheism.

Facebook is the blogger's primary platform.

"I criticize Islamic militants. I criticize our government. And basically I write about women's rights," he says.

Azad says he was only 13 years old when he narrowly escaped a kidnap attempt by Islamist militants.

Today, the writer speaks to CNN from exile in Germany. He fled here last autumn after he appeared on hit lists posted online by extremists.

"They openly declared I would be their next target," he says.

He asks CNN not to publish the name of the town he is now living in, because he continues to receive online death threats.

Exiled Bangladeshi blogger Ananya Azad (center) walks with two fellow "free-thinkers" in Germany.

Azad shows a photo of his father, taken moments after a machete attack on February 27, 2004. The man's white shirt and face are bathed in blood, and he appears to be trying hold his wounds shut as a police officer helps escort him away.

Before he passed, the elder Azad lost vision in one eye and also lost the ability to eat solid food after the attack.

"He is my inspiration," his son says.

Determined to carry on his father's work, Azad says he continues to denounce the militant groups that have been killing his friends in Bangladesh.

"Thay are very strong, they have financial support ... but I have a pen and this is my weapon. I cannot hurt anyone. But I can give much more knowledge to everyone," Azad says.

The atheist exile's defiance is echoed by the Muslim cleric in the Bangladeshi capital.

"I'm not afraid of the terrorists," says Sufi Imam Ahmed Reza Faruqi.

"I will not fear the darkness."