COMBINED RUC and British army checkpoints were reinstated in many parts of Northern Ireland yesterday in what was described as a precautionary measure due to recent uncertainty.
Evening rush hour motorists experienced delays in some places because of the vehicle checkpoints.
Security gates were closed last night in many towns across the North, including Armagh, Banbridge, Lurgan and Portadown.
An RUC statement said "anti terrorist precautions" had been increased in view of the recent uncertainty over the intentions of paramilitary groups, especially on the republican front.
The UDA had warned on Monday that it was placing its units on alert, in the belief that a resumption of IRA attacks in Northern Ireland could be imminent.
A delegation of Ulster Democratic Party (UDP) politicians visited UDA prisoners in the Maze yesterday and reported that the inmates had expressed frustration at the IRA's ability to continue attacks on British cities with impunity.
However, a UDP spokesman said the prisoners also expressed their full backing for the party's strategy within the multi party negotiations in the pursuit of a political settlement.
This was taken as indicating that the loyalist ceasefire continued to hold.
The spokesman said the prisoners had endorsed the decision to put UDA units on alert. They feared that an imminent return to IRA violence could put the loyalist communities under threat.
Meanwhile, the IRA in south Armagh was reported to have issued a statement yesterday denying that there was a split in the organisation.
The statement described as "utter rubbish" a newspaper report at the weekend about disagreement between the IRA leadership and the south Armagh membership.