The incident followed two weekend deaths from terrorism, with loyalists killing a member of Sinn Fein and the victim of a republican 'punishment squad' dying of his injuries.
The rocket attack was launched at Belfast's Crumlin Road prison, which houses both republican and loyalist remand prisoners. The target was the A-wing canteen, where republicans were dining at the time, but the missile missed and struck the roof.
Prisoners were immediately returned to their cells while a major security operation was launched outside the jail, which is close to the hardline loyalist Shankill Road area.
A taxi hijacked in the district a short time earlier may have been used in the incident.
A telephone caller who used a recognised Ulster Volunteer Force codeword claimed the attack in the name of the 'Loyalist Military Command', saying the target had been 47 republicans in the canteen. He added that it was intended as retaliation for the IRA bomb which killed two loyalists in a prison canteen in November of last year.
It is assumed that an RPG-7 rocket was used in the attack. Although these weapons are more often associated with the IRA, loyalist groups have a small number of them and have used them on several occasions in recent years. They are believed to have reached the extreme Protestants in a shipment of arms from South Africa.
The Sinn Fein member who died at the weekend was the fifth member of the party to be killed by the illegal Ulster Defence Association in the last 18 months. Malachy Carey, 36, was shot twice as he waited for his girlfriend in the Co Antrim town of Ballymoney on Saturday night.
His injuries were at first thought to be not life-threatening, but his condition deteriorated sharply overnight. Police said a man was being questioned about the killing.
Mr Carey, who had served a lengthy prison sentence for IRA offences, was a Sinn Fein candidate in a council election three years ago. Police said he had been warned three years ago that his name was on a loyalist death list.
The second man to die was a 36- year-old Londonderry man whose legs were amputated following an IRA punishment shooting in the city last Tuesday night. He was John Collett, who had been on a life support machine since the shooting and the emergency operation in which surgeons could not save his legs.
The RUC said the IRA had used an improvised flame thrower to attack an Army look-out post in Crossmaglen, south Armagh on Saturday night. The post was sprayed with a highly flammable mixture from a slurry tank which was pulled into position by a tractor. No one was injured.
Two men in their twenties will appear in court today charged in connection with a Belfast city centre bombing, police said. No one was hurt in the double explosion in a multi-storey car park in the Chicester Street district last Wednesday.