Tensions were high in north Belfast last night after three gun attacks in two days left two men dead and another critically injured.
Sinn Fein has urged nationalists to be vigilant, while the SDLP and Alliance called for an immediate end to the shootings.
The DUP expressed "grave concern" about the deteriorating security situation.
No group has admitted responsibility for yesterday's shootings but loyalists have been widely blamed. A 30-yearold workman from Co Derry was shot dead at 4 p.m. in the Protestant Monkstown Estate on the outskirts of north Belfast.
Two men shot the victim several times in the head and body as he worked on houses for the Housing Executive in the Devenish Drive area. The assailants fled on foot. The man's body was still at the scene last night. He was named locally as Mr Gary Moore, who lived in Limavady with his girlfriend and two young children.
Fifteen minutes later, a 22year-old Catholic taxi-driver was injured in an attack in the Oldpark Road in north Belfast. The man was sitting in his car outside Park Taxis when a motorcycle pulled up and a gunman opened fire, shooting him several times through the window. Detectives recovered a black and grey motor-scooter abandoned near the scene of the shooting. It was hijacked in the area a short time before the attack.
The victim was named last night as Mr Paul Scullion. He was "critical but stable" in hospital.
Both RUC sources and Sinn Fein said they believed loyalists were responsible. Sinn Fein Assembly member Mr Gerry Kelly said some loyalists had wrongly blamed republicans for the killing on Tuesday night of a Protestant taxi-driver, Mr Trevor Kell.
Mr Kelly said there was no evidence of republican involvement in the shooting.
"Nobody in nationalist north Belfast knows anything about it. History shows that loyalists feud among themselves and then it all ends with attacks on Catholics."
However, loyalist paramilitaries denied that the killing of Mr Kell was part of their feud A 35-year-old father of three, Mr Kell was shot as he went to collect a fare in the loyalist Oldpark area late on Tuesday night.
Mr Billy Hutchinson, whose Progressive Unionist Party has links with the Ulster Volunteer Force (UVF), dismissed speculation that the murder was linked to the dispute with the Ulster Defence Association (UDA) which has claimed seven lives since August.
Intense negotiations between the two groups have been continuing in recent weeks in an attempt to reach a settlement.
A joint statement has been issued on behalf of the Ulster Freedom Fighters (a cover name for the UDA), the UVF and the Red Hand Commando.
It said the three groups were investigating the death of Mr Kell. "We are convinced that Mr Kell's death has nothing to do with the so-called loyalist feud."
Mr Kell worked for a taxi firm based on the staunchly loyalist lower Crumlin Road.
Security sources said he was not linked to any paramilitary organisation and speculated that he was a random victim as his killers would not have known which driver would answer their call. A police spokesman said detectives have yet to rule out any possible motive for the attack.
Mr Kell's widow, Margaret, the mother of three children aged 10, 11 and 14, said her husband had just started working on Monday night. Local politicians condemned the killing. The Democratic Unionist Party MLA for north Belfast, Mr Nigel Dodds, said: "The murder demonstrates the need for the RUC to be kept at full operational capacity and not to be neutered for political reasons".
The leader of the Alliance Party, Mr Sean Neeson, called on the "community at large to help the police and bring to justice those responsible for this cruel murder".