The minority Shia Muslims in Bogra's Shibganj upazila have never felt threatened living in the Sunni-dominated area. On the contrary, they have always lived peacefully with their Sunni brothers and sisters for decades.

But now a sense of fear has gripped them following Thursday's gun attack inside a Shia mosque by unknown assailants. The shooting killed the muezzin of the mosque and injured three more, including the imam.

The history of peaceful coexistence between the two sects in Shibganj goes back to 1982. In that year, Abu Jafar Mandal, a freedom fighter, attended a lecture in Dhaka. The lecture was given by the then foreign minister of Iran who was also a Shia scholar.

Though from a Sunni family, Jafar, then in his 30s, was inspired by the lecture and started to follow Shia faith, he told The Daily Star yesterday.

Over time, more people joined, and at present there are at least 110 Shia families (some 600 people) in the three unions under Shibganj upazila. The upazila has some 6,000 Sunni followers in about 2,000 families, he added.

Jafar, who is believed to be the first Shia follower in Shibganj, said: “I never faced any problem because of my faith, let alone facing a threat in the last three decades.”

There has been such a harmony between Shia and Sunni there, like in rest of the country, that Sunni Muslims sometimes offer prayers in the Shia mosque that came under the gun attack.

Given the past record, locals, victims and their families said they did not believe the shooting had anything to do with their sect.

Police are clueless about the attackers or their motive, but locals from both the communities see it as an act of Islamist militants.

The shooting happened around 5:45pm when 30 to 40 people were saying their evening prayers.

At least three gunmen stormed the mosque at Atmul union, locked the main entrance from inside and shot at the praying people at random before fleeing, police said, quoting locals.

Cops yesterday collected evidence, including eight bullet shells and the lock used to close the mosque entrance. Two people -- Anwar Hossain, 48, and Jewel, 25 -- were detained for questioning.

According to the US-based SITE Intelligence Group, Islamic State has claimed responsibility for the attack.

“The Islamic State (IS) claimed credit for the November 26, 2015 attack on a Shi'ite mosque in Bangladesh's Bogra district,” SITE, which monitors jihadist activities, said in a tweet at 3:00am yesterday.

The claim could not be independently verified.

Thursday's was the second attack on the Shia community in Bangladesh in just over a month.

On October 24, their Ashura gathering at Hossaini Dalan in the capital was bombed, killing two people and injuring about 100 others.

That attack too bears testimony to the harmonious coexistence of Shia and Sunni in the country, as both the dead and most of the injured were Sunnis, The Daily Star found after talking to the families.

Hossaini Dalan is regarded as the headquarters of the Shia Muslims in the country, and the attack happened about half an hour before the traditional Tajia procession was to be brought out to mark the holy Ashura.

The day commemorates the martyrdom of Hazrat Imam Hussain (RA), and the Shia community in Bangladesh has been observing the day for centuries, but never before came under any attack.

The black flag Jafar hoisted at the Imamia Library, which he founded in 1982 in Shibganj, protesting the Ashura attack still flies.

“We are worried after all these years. We urge the prime minister and law enforcers to take the matter seriously and help us live peacefully,” said the 65-year-old.

He said some students of local Qawmi madrasas travelled to Chittagong for attending religious programmes recently, and there might be a connection here.

Last year, two religious gatherings were held in the upazila's Gopinathpur and Aliarhat Bazar. “Speakers censured some religious practices of Shia's in those meetings,” said Jafar.

“We live like brothers and sisters and even Sunnis attend prayers in our mosque and the vice versa.”

Thirty-five-year-old Idris Ali is just one proof of such harmony. He is a Sunni, but his uncle Aftab Ali is a Shia.

Aftab, 45, is one of the three injured in Thursday's shooting. He was hit in the back and was released from hospital yesterday.

Post mortem report shows Moazzem Hossain, 70, was hit in the head from behind and the bullet exited through his left eye. Another bullet hit his left leg. He died at Shaheed Ziaur Rahman Medical College Hospital soon after the shooting.

Some managed to duck, others lay on their backs on the floor.

The imam, Shahinur Islam, was hit by a bullet below his waist and is said to be out of danger.

Asked about the attackers and their motive, Inspector (inquiry) Kamruzzaman Miah of Shibganj Police Station, who is investigating the case, said it was too early to comment.