A loyalist councillor has been arrested and questioned in connection with the murder of Mr Daniel McColgan in Antrim on Saturday.
Security sources confirmed the councillor and another man were arrested on Monday night by detectives investigating the shooting of Mr McColgan in Rathcoole, on the outskirts of Belfast.
There was a heavy security presence in north Belfast again yesterday. Police and army vehicles sat outside schools and patrolled the area from early morning until closing time in response to threats made against Catholic teachers and other staff working in the area.
The threats came from the Red Hand Defenders, a cover name for the UDA, which had also said it would consider Catholic postal workers "legitimate targets".
The Northern Ireland Office said that about 300 police officers and 450 British soldiers were involved in the operation.
A caller claiming to represent the INLA threatened Protestant workers at the Marks & Spencer distribution centre at Mallusk in Co Antrim. The police said they were increasing the number of patrols in the area in response to the threat, while Marks & Spencer said it was currently reviewing its own security procedures.
Meanwhile, the Northern Ireland Housing Executive said it had received 114 requests for housing from people who said they had been made homeless due to civil disorder or intimidation in north Belfast since July.
A spokesman for the Housing Executive said the requests came from throughout the north Belfast area and from both communities.