The 52-year-old man arrested over the murder of British parliamentarian Jo Cox was described by neighbours as a quiet loner with a passion for gardening. Family said he had a history of mental illness.

The suspect, who lived close to the scene where Cox was shot and stabbed in her constituency near Leeds in northern England, was named by media as Thomas, or Tommy, Mair. There have been no charges in connection with the murder.

Next-door neighbour Diana Peters, 65, told Reuters that she had known Mair since he was a boy and he never had visitors.

"I'm totally devastated - I didn't want to believe it. He's been very helpful to me. Anything I asked him to do he did very willingly and sometimes without my needing to ask," Peters said.

"I saw him the day before. I was taking my cats to the vet and he came and asked me how they were," she added.

Mair had taught English to foreigners in the local community for several years and was brought up by his grandparents, she said. His mother is now in a local care home, she added.    

Mair's house was taped off with police guards outside on Friday in an estate of small houses, many draped with English flags because of the European soccer tournament.  

The Guardian newspaper said police were investigating Mair's political affiliations following witness accounts that the suspect shouted "Britain first" as he launched the attack. Britain votes on June 23 about whether to leave the European Union and campaigning has sometimes been acrimonious.

There were also reports, linking Mair to right-wing groups in the US and South Africa.

Family members said that Mair had not expressed strong political views, media reported.

Mair's half-brother, Duane St Louis, 41, told ITV television he believed his brother "wouldn't hurt a fly", according to the British Press Association.

He told the Sun: "He's never expressed any views about Britain, or politics or racist tendencies. I'm mixed race and I'm his half-brother, we got on well."

"He has a history of mental illness but he has had help," the Guardian quoted his brother, Scott Mair, as saying. "I am struggling to believe what has happened. My brother is not violent and is not all that political. I don't even know who he votes for."

The Press Association said the half-brother was speaking after it emerged that a Thomas Mair, from Batley, was named in a 2006 edition of the Springbok Cyber Newsletter, produced by the hard-right Springbok Club, a group which has called for a return to apartheid-style government in South Africa.

Reuters could not confirm the report.

A US civil rights group the Southern Poverty Law Center (SPLC), based in Alabama, said on its website that it had obtained records showing a Thomas Mair had links with the neo-Nazi organisation National Alliance (NA) dating back to 1999.

The SPLC posted images showing what it said were purchase orders for books bought by Mair, whose address is given as Batley, from the NA's publishing arm National Vanguard Books in May of that year. The orders included a manual on how to build a pistol, it said. It was not known if the orders were delivered.

"We had never heard the name Thomas Mair before. When they announced that he was a suspect, we ran his name in our file and found these documents. We don't know anything more about him," Heidi Beirich, Intelligence Project Director at the Southern Poverty Law Center told Reuters.

Neighbours were quoted by media as describing a man who had lived in the same house for decades and helped locals to maintain their flowerbeds.

The Guardian said that in 2011, Mair was photographed by the local newspaper volunteering in nearby Oakwell Hall country park.

The previous year he was quoted in the Huddersfield Daily Examiner, saying he had begun volunteering after attending Pathways Day Centre for adults with mental health issues.

"I can honestly say it has done me more good than all the psychotherapy and medication in the world," he was quoted as saying.

According to the Sun newspaper, Mair's half-brother said the suspect was obsessed with personal hygiene. He added: "He was always cleaning himself. He cleaned himself with Brillo pads." He was quoted in the Mirror as saying Mair had been diagnosed with obsessive compulsive disorder.

The half-brother said: "He never married. The only time I remember him having a girlfriend was as a young man, but a man stole her off him. He said that put him off for life."

Local people told the Press Association they did not think Mair had a job or drove a car.

David Pickles was quoted as saying: "He's lived there longer than me and I've lived here since 1975.

"He's just quiet. He kept himself to himself. He lived by himself. He's been on his own for about 20 years. I've never seen a lot of people visiting or anything like that, but he likes gardening. He did a lot of people's gardens round here. But he did it quietly."

Another resident, who declined to be named, was quoted in the Guardian as saying Mair had never been in trouble with police, "practically lived in the library" and liked to write his own stories.

"He was obsessed with books," she said. "His house is full of them."-Reuters