A number of people were being questioned by RUC detectives last night following the murder of Mr Richard Jameson near Portadown, Co Armagh, on Monday evening.
The 46-year-old businessman and building contractor, who security and loyalist sources say was a UVF leader, died after he was shot in his jeep outside his home on the Derrylettiff Road, five miles from Portadown.
Mr Tom Craig, the RUC south region assistant chief constable, said the killing was callous and cold-blooded. Several people from the mid-Ulster area were being questioned about the murder, but Mr Craig would not specify the number in custody.
Mr Jameson's funeral will take place near Portadown tomorrow from Tartaraghan Church of Ireland parish church, a few miles from Mr Jameson's home.
Mr Bobby Jameson, a brother of the murdered man, said there would be no paramilitary trappings at his funeral. He denied his brother was involved in the UVF. He said he was a hardworking family man.
"Richard had only one fight and that was the fight against drugs. He stood up against drugs and the hooligan element in Portadown," said Mr Jameson.
"He detested drugs and the people supplying them. These people are ruining young people's lives. It's time something was done. The police know who they are and they should put them away," he told BBC Radio Ulster.
The North's First Minister, Mr David Trimble, visited the murdered man's family yesterday. Afterwards he warned that speculation about an inter-loyalist feud as a result of the murder was only heightening tension, and appealed for no retaliation.
"I condemn entirely those responsible for the murder of Mr Jameson. I would appeal to people to leave it to the police to investigate this murder," he added.
The Northern Secretary, Mr Peter Mandelson, said people did not want to see "a return to the dark days of this sort of violence".
Mr David Ervine of the Progressive Unionist Party said the murder was probably carried out by a "disparate group masquerading as loyalists simply to give cloud cover to the nefarious trade of drug-dealing".
His PUP colleague, Mr Billy Hutchinson, blamed the LVF for the murder. He said Mr Jameson was an upright man who was opposed to local elements involved in drug-dealing.
Mr Hutchinson said there were a number of politicians shedding "crocodile tears" about the murder who had also praised the LVF for handing over some weapons to Gen John de Chastelain's decommissioning body. "Well, the LVF still managed to get a weapon to kill Richard Jameson," he added.
The Sinn Fein leader, Mr Gerry Adams, deplored the killing, and offered his sympathy to the Jameson family. He described the LVF gesture on weapons as a "stunt".
DUP MLA Mr Paul Berry said the murder was cowardly. "It just makes me sick to think that there are people in our society that would stoop so low and carry out such an attack," he said.
Mr Andrew MacKay, the Conservative spokesman on Northern Ireland, said if it were established that the LVF was involved their prisoner releases should be halted.
"A key element of the Belfast Agreement was an end to violence for good, and we must never differentiate between so-called internal housekeeping and the murder of members of the public and the security forces," said Mr MacKay.
The murder was also condemned by the SDLP, the Ulster Democratic Party, the Workers' Party, and the Northern Ireland Human Rights Bureau.
