The family of a Pakistan-born man who died following a suspected “religiously prejudiced” attack linked to sectarian tensions within the Scottish Muslim community have spoken of their fears for their own safety.

Shopkeeper Asad Shah, 40, was found seriously injured near his store in the Shawlands area of Glasgow around 9pm on Thursday and was later pronounced dead on arrival at hospital.

Hours earlier he had wished Christians a 'Happy Easter' in a social media post, and he had previously appeared to speak out against extremism.

Shah was a member of the Ahmadi movement, a minority denomination of Islam which is regarded by some orthodox Muslims as heretical because they believe that founder Mirza Ghulam Ahmad – who died in 1908 – is the messiah and a prophet.

In some predominantly Muslim countries Ahmadis are persecuted, and in Pakistan a constitutional amendment passed in 1974 declared Ahmadiyya non-Muslims.

Police have confirmed that a 32-year-old man arrested after the death of Shah is a Muslim and officers said the attack is being “treated as religiously prejudiced”.

A family member who asked not to be named told the Sunday Herald: “We have been advised by the police not to speak about it, particularly about our names and locations, because there is a security threat.”

The relative added: “Actually, we cannot describe what we are going through. We are heartbroken.”

Shah’s father spoke of his shock yesterday and revealed another of his sons saw the attack.

He said: “I just can’t speak, we are in shock here. I don’t know the details of what happened, I wasn’t there but my other son saw everything. He was there at the time, and he was injured too but only slightly. I’m sure you can imagine how we are all feeling.”

There is only one official place of worship for the Ahmadiyya community in Scotland – the Bait-ur-Rahman Mosque in Glasgow’s west end. A second mosque is due to open in Dundee this year.

Sources at the Glasgow mosque say there are only 500 Ahmadi in Scotland, with around 400 of them based in and around Glasgow. Many of them knew Asad Shah.

Dr Sultan Ahmad, 38, said: “He was a lovely chap. An absolutely fantastic guy. Very friendly. We’re all very sad. It was a horrible thing to happen, that came from nowhere. It was uncalled for.”

Fareed Ahmad, National Secretary for External Affairs at Ahmadiyya Muslim Community UK, described the killing as “completely brutal, horrific and unjustified”.

“Such murders are a cause of extreme grief and sadness and our prayers are with the victim and his family,” he said.

Ahmad also issued a plea to authorities to protect the Ahmadiyya community.

“In any society, all members of the public have a right to safety and it is up to the government and police to protect members of the public as best they can,” he added.

“In this context it is up to the government to root out all forms of extremism and the Ahmadiyya Muslim community has been speaking about the importance of this for many years.”

Imam Daud Ahmad, 60, who is the spiritual leader at the Bait-ur-Rahman Mosque, indicated that there are deep divisions between different Muslim denominations.

He said: “The main difference is, according to Islamic traditions, a reformer is due to come in latter days after the Prophet Mohammad.

“We believe Mirza Ghulam Ahmad, the founder of the Ahmadiyya community, was the same reformer about whom the prophecy was made. We have accepted him.

“Officially he announced the foundation of the community on the 23rd of March 1889 in a small town called Qadian.

“This is the basic belief we have. There is no new religion. It’s the same Koran, same teachings, and same prayers as other Muslims. We also go on pilgrimage to Mecca, like other Muslims.

“But the difference is they are still waiting for someone to come. We believe he has already come.”

The Imam declined to comment on the death of his friend Asad Shah but added: “The truth always faces opposition from people. They hate us because we have brought a message they cannot digest...but it doesn’t mean somebody should be murdered.”

Human rights lawyer Aamer Anwar, who has been working to alleviate tensions in the Muslim community, said: “Sadly in our beautiful city there has always be those hell bent on bigotry and violence, but as a Sunni Muslim I proudly stand with my brothers and sisters of the Ahmadiyya community to say 'not our name'.”

Glasgow Central Mosque issued a statement about the death of Shah which offered condolences to his family and said: “This type of criminal behaviour is abhorrent and unacceptable and the Mosque stands shoulder to shoulder with all communities in order to eradicate this kind of intolerance from our society.”

Vigils have been held for Shah in the community in Glasgow’s south side where he worked.

Around 500 people joined in a silent gathering in Shawlands on Friday night, with some laying flowers at a sign on the ground which said: 'This is not who we are'.

A steady stream of people went to the area on Saturday and a group of around 150 took part in a sombre vigil organised by teenagers on social media.

A fund-raising page set up on the GoFundMe website in support of Shah's family has raised around £30,000.

A funeral for Shah is likely to be held at Bait-ur-Rahman Mosque when the body is released by the authorities.

A source at the mosque said: “Obviously the body has not been released by police – it’s an ongoing enquiry and there will be a post mortem – but when that happens there will be a funeral here.”

Asad Shah is expected to be laid to rest in a specific area of a Glasgow south side cemetery set aside for Ahmadiyya Muslims. The source added: “There is a cemetery in Cardonald. The council has given us space there. We are now separate. There are four or five people already buried there.”

Local SNP MP Stewart McDonald said the city had lost one its “most warm-hearted souls”.

It is understood the 32-year-old man who was arrested was in police custody last night.

A spokesman for Police Scotland said: "A report will be sent to the procurator fiscal. A 32-year-old man is due to appear in court on Tuesday."