Sunday, August 16, 1998 Published at 13:25 GMT 14:25 UK
Nine children among 28 dead
Nine children, 13 women and six men were killed by the car bomb
Click here to watch BBC News 24 coverage of the Omagh bombing.
The Northern Ireland peace process is under strain following the Omagh car bombing which left 28 dead and more than 200 injured or maimed.
Nine of the dead are children - five girls including an 18-month-old baby and four boys. Fourteen women, including one who was pregnant, and five men were killed.
Among the dead were three generations of the same family. The three women from Augher, County Tyrone, were a 65-year-old, her 30-year-old daughter, who was heavily pregnant, and her 18-month-old toddler.
No group has admitted responsibility, but suspicion has fallen on dissident republican groups opposed to the current ceasefires.
"No stone will be left unturned until we bring these people to justice," said Mr Flanagan.
He said the investigation would concentrate on the group known as the Real IRA.
"They are out to murder people for the sake of murdering people. That's exactly what they did yesterday," he told the BBC's Breakfast with Frost.
'Blast of evil'
Before heading off for Belfast, he condemned the attack as a "blast of evil" perpetrated by a tiny group of fanatics.
"I just kept thinking last night of those poor people, those poor murdered people," said Mr Blair.
"Yesterday at this time this was just another normal day for them, leading normal lives with the normal balance of cares and worries and hopes, and now by this blast of evil their lives are gone."
During his stay in Belfast, Mr Blair is meeting Northern Ireland political leaders
The government has insisted it will not let the bombing undermine peace efforts.
He added that "we must all redouble our efforts" to achieve the goals set out in the Good Friday Agreement."
'No retaliation' plea
Ken Maginnis MP, of the Ulster Unionist Party, urged "no retaliation" by loyalist paramilitaries for the bombing.
Mr Maginnis said the people of Northern Ireland "want to see a peaceful way forward with both traditions accommodating each other".
"There should be no retaliation except by the lawful authority, and that is the two governments, particularly the Irish Government," he told the BBC's Breakfast with Frost.
One source said they were not allow anyone to steer their agenda for them.
The Ulster Democratic Party, which speaks for the biggest loyalist paramilitary group, the UDA, has already called for calm.
"The Ulster Democratic Party deplores the mindless bombing in Omagh and the senseless loss of life but urges loyalists to remain calm and not be drawn into any retaliatory action which would play into the hands of these republicans intent on wrecking this peace process," it said.
Martin McGuinness, the chief political negotiator for Sinn Fein, said politicians involved should not allow the bombing to derail the peace process.
"It is time for us to keep our nerve, it is a time for us to give sensible political leadership, it is a time for us to band together and to show these people that they aren't going to succeed in destroying the peace process," he said.
The RUC has set up a casualty bureau to deal with inquiries from the public. The number is 01232 673371.
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