A bomb found near a primary school was designed to maim and kill, police said.
Two controlled explosions were carried out on the device — understood to have been an under-car booby-trap bomb — by Army technical experts on Monday afternoon.
It is believed the device may have fallen off a vehicle.
Police investigating a possible target for the bombers on Monday night examined two vehicles in east Belfast. Halcombe Street and Middlepath Street in the lower Woodstock area were sealed off from about 8pm.
It is not yet clear who the target of the bomb was or which group was responsible, although dissident republicans have used similar devices in the past. It was found just before noon at Ballymagarry Lane near Springhill Primary School, north Belfast.
A number of houses had to be evacuated, and three other primary schools — Springfield, Harmony and Forthriver — were advised to keep children indoors during the security alert.
Those evacuated from houses close to Ballymagarry Lane were allowed to return home on Monday night.
A number of items were taken away for forensic examination.
Ballymagarry Lane is a busy access route, leading to a large housing development.
The residential area is popular with young families. Many residents were stranded in their homes throughout Monday, with those who left prior to the alert unable to return to their homes.
A police spokesman on Monday said: “Detectives from the PSNI's Serious Crime Branch are investigating the circumstances surrounding the discovery of a viable explosive type device discovered in north Belfast earlier today. At this stage police believe that this could have been an under-car booby-trap designed to kill and maim.”
DUP MLA for North Belfast William Humphrey said it was fortunate no one was hurt.
He said: “Those responsible have been entirely reckless and did not care who suffered the consequences of their actions. We are indebted to the PSNI and Army bomb disposal officers who cleared this security alert.
“Those responsible for this deplorable device must be stopped.”
He urged anyone with information to pass it to police.
A Presbyterian church hall was opened for residents with refreshments.
Rev Brian McMillen said locals were saddened and frustrated by the security alert.
He said: “We don’t want to go back to this again, that’s how everybody feels.” Care worker Susan Mullan said a young person with learning difficulties she works with was prevented from getting home.
“My grandson, who is three, and eight-year-old granddaughter have been out of their home since this morning and it’s now 6pm,” she added. “People don’t want to see this. I was brought up round here and it’s a very quiet area.”
Another said the area is popular with young families.
“It’s terrifying this has happened,” she said. “There are loads of kids round here. The people who did this need to take a look at themselves.”
Ballymagarry Lane was expected to remain closed overnight.