A car bomb abandoned by unionist paramilitaries near Belfast city centre last week was destined for the city's St Patrick's Day carnival, it is believed.
The car bomb was found shortly after 8pm on St Patrick's night parked in the south of the city.
The device, made up of a gas cylinder, fire extinguisher and incendiary devices, was similar in construction to the UVF car bomb planted at the Auld Lammas Fair in Ballycastle in August 2001.
It could have caused a giant fireball to rip through the city centre.
Both devices appear to have been targeting festivals where large crowds of people were gathered in the street.
``It's unclear whether the bomb was intended to disrupt the St Patrick's Day carnival or to explode while people were packed into the city centre,'' the security source said.
Francie Mackin, who had to evacuate customers when the car bomb was found outside his bar, said police at the scene told him the device could have caused widespread damage.
``When the police first told me there was a bomb outside I thought they were joking. When no one in the bar owned the car we evacuated the place immediately,'' Mr Mackin said.
``I actually looked into the car and could see a gas bottle and fire extinguisher on the back seat with a white box taped on top of them.
``The PSNI told me the target for the bomb was the St Pat-rick's Day carnival.
``I asked a police man how much damage the explosion would have caused and he told me it would have destroyed anything or anybody around it.''
Sinn Féin south Belfast assembly member Alex Maskey described the incident as ``deeply worrying''.
``It would appear that loyalists in south and east Belfast are escalating their activities far beyond pipe bombs,'' he said.
``If this bomb was destined for the city centre then it could have caused untold carnage.
``It seems clear that one of the loyalist organisations was intent on creating mayhem.''