The planting of a pipe bomb discovered outside a Territorial Army base has been described as a "reckless throwback action to a past we do not want".
The device sparked a day-long security alert in leafy south Belfast.
It followed two more security alerts before noon yesterday.
Two controlled explosions were carried out in north Belfast and Holywood.
A beer keg spotted in a car on the Hillview Road in the north of the city was later described as a hoax while the Holywood alert was declared as "nothing untoward".
The Malone Road was closed between Adelaide Park and Cranmore Park for over seven hours after the discovery of the pipe bomb.
The area was jammed with cars during rush hour and some bus services were suspended.
Schoolchildren from Methodist College said they were scared and worried about their return journey home.
First-year pupils from two other schools stood watching as police rerouted traffic, calling home to reassure worried parents. The viable device was made safe by Army bomb experts and the alert ended just after 5pm.
Local councillor and member of the Belfast District Policing and Community Safety Partnership Claire Hanna said such activity was not wanted.
"This deliberate behaviour is unwelcome and a reckless throwback action to a past we do not want.
"This is very disruptive for the people trying to live their everyday lives. These events are very sinister and unwanted here."
In Holywood, memories flooded back for a community still shaken from a Real IRA bomb in April 2010.
A security alert sparked by a suspect object outside Palace Barracks Army base in Holywood yesterday morning resonated with the residents still "haunted by the past". The barracks also houses the headquarters of MI5.
One resident said when the police knocked on her door yesterday to tell her family to stay indoors during the alert, "memories of forensics in white suits scouting her garden" for shrapnel came flooding back.
"While people remain determined to cause harm, there is always the possibility it can happen again and that's the worst part.
"It puts the security situation literally on your doorstep," the mum-of-three said.
At one point, officers considered evacuating an elderly care home into the neighbouring graveyard.
A controlled explosion was carried out by the bomb squad before noon on the Old Holywood Road.
The object was described as "nothing untoward".
Both alerts came after a number of families in north Belfast had to to leave their homes after the discovery of a suspicious object in a hijacked Volkswagen Sharan at around 1am yesterday on Hillview Road, just off the Crumlin Road.
Army technical officers carried out a controlled explosion at 8am and the object was declared a hoax. Greater Shankill DUP councillor Brian Kingston condemned those behind the hoax.
He said: "Given where this car was stolen, suspicion will fall on dissident republicans who are constantly seeking to increase tensions and destabilise society."
"This and other recent sectarian incidents, including the telephoning of threats against Catholic schools and scrawling of threats against Protestant workers, are to be utterly condemned."