The news was welcomed in almost all quarters, though the British and Irish governments both declared that the move would not affect the intensive police investigation into the attack, which is under way on both sides of the border.
It was also made clear that anyone jailed in connection with the attack could not expect to benefit from the Good Friday Agreement's early prisoner- release scheme. The first inmates to be freed under the scheme will be out this week.
In Omagh, a Unionist councillor said the ceasefire was "music to my ears", while a nationalist representative added: "All I can say is thank God." Only one of the various republican and loyalist groups, the Continuity IRA, has yet to declare a ceasefire.
Although there is concern that some in the Real IRA's ranks might conceivably attempt to continue violence, the security assessment is that the seven members of its ruling "army council" and the organisation as a whole have genuinely decided to call it a day.
The declaration had been expected for some time, following signs of disarray and even panic within the organisation, which was unprepared for the wave of public condemnation sparked off by the Omagh bomb.
The organisation faced huge challenges on three fronts. Firstly it was facing, and still faces, a determined push from the security forces to put its members behind bars, using the specially tailored laws approved by last week's special sessions of Westminster and the Dail.
Secondly, it was facing immense public disapproval. This manifested itself in the waiving of human rights concerns and approval of the new laws, with the overwhelming weight of opinion in both north and south supporting whatever was thought necessary to shut down the organisation and prevent more Omagh-style attacks.
Thirdly, the mainstream IRA appeared to be shaping up to move against the group. During a highly co-ordinated 90-minute period last week scores of Real IRA members and supporters were visited by IRA members who told them they were in violation of IRA rules. Some were reportedly told they would be shot if they continued their activities.
The man regarded as the Real IRA's leader, who lives in the Dundalk area of the Republic, was visited by a well-known senior IRA member from west Belfast who left him in no doubt of the fate that awaited his organisation if it persisted in its campaign.
Regardless of the ceasefire, the authorities are pledged to keep after the Real IRA. Surveillance of suspects is said to have been particularly intense since Omagh.Reuse content