The suspected leader of a gang that abducted and tortured a businessman near the Irish border has died during a raid by police at his home in Derbyshire.

Cyril McGuinness, who was in his 50s and had dozens of criminal convictions, died on Friday morning. McGuinness, originally from the Derrylin area of Northern Ireland, went by the nickname “Dublin Jimmy”.

As part of a coordinated operation by UK and Irish police, more than a dozen homes and business premises were searched in Ireland, Northern Ireland and England in connection with the kidnap and brutalisation of Kevin Lunney. The case shocked Ireland and exposed lawlessness along the border.

At a press conference in Dublin, the Police Service of Northern Ireland assistant chief constable Mark Hamilton described the death as “regrettable”.

He added: “The PSNI commissioned a search in England with the support of the police officers there and a report has been that a man has died, which is very regrettable. That is now a matter of investigation in England separate to this ongoing inquiry.”

Dozens of gardaí searched five properties in Cavan, four in Dublin and three in Longford, while PSNI officers searched five properties in County Fermanagh, Northern Ireland.

Kevin Lunney was abducted and tortured in September. Photograph: BBC Spotlight/PA

McGuinness’s home was searched by officers from Derbyshire police. It is thought McGuinness, who was well known to authorities on both sides of the Irish border, was “lying low” in England due to the intense public and police focus on the Lunney case.

Earlier, DCI Julie Mullan of the PSNI said the coordinated raids were a “significant” operation. “This was a truly horrific crime and we continue to work closely with our colleagues in An Garda Síochána and now also Derbyshire constabulary to try and bring the perpetrators to justice,” she said.

Masked men ambushed Lunney, 50, on 17 September outside his home in Derrylin, Co Fermanagh, and tortured him for about two hours before dumping him across the border in Co Cavan.

It was the latest and most brutal act in an eight-year campaign of intimidation against executives of Quinn Industrial Holdings, a building materials company that straddles the border. Lunney is the company’s operations director.

In a BBC interview earlier this week, Lunney recounted how the gang ordered him and other executives to resign before performing a checklist of sadistic acts that left him in agony. They broke his leg, stabbed his fingernails, poured bleach on the wounds and carved QIH on his chest.

QIH is a remnant of a business empire built by Seán Quinn, an entrepreneur who became Ireland’s richest man before losing his fortune and companies in a bet on a toxic bank.

Quinn, 71, accused QIH executives of betraying him. He has denied any involvement in the intimidation campaign, condemned the attack on Lunney as barbaric, and said he feared being blamed.

QIH’s chief executive, Liam McCaffrey, this week told the garda commissioner, Drew Harris, that a failure to find those responsible would leave the community in fear and imperil the local economy.

Micheál Martin, the leader of the Fianna Fáil opposition party, called for a cross-border taskforce to tackle increased crime in the area.

Father Oliver O’Reilly, the parish priest of Ballyconnell in Co Cavan, where there have been many incidents of intimidation against QIH executives, said a mafia-style campaign had shrouded the community in fear.

“The untouchables in the region have to be called to account for their actions. They’re still untouchable. No one has been arrested,” he said.

In a separate operation near the border on Thursday, gardaí from the state Criminal Assets Bureau raided homes and business premises of two Irish men suspected of involvement in the deaths of 39 Vietnamese migrants who died while being trafficked to England.

The police seized several vehicles and other property. The suspects have reportedly been under investigation since last year over alleged smuggling across the Irish border, an investigation that preceded the discovery of the bodies in a lorry in Essex on 23 October.