Chief Constable Matt Baggott has warned of a surge in dissident republican activity after a bomb partially exploded under a shopping centre in Belfast city centre.
A terrified driver was forced to bring up to 130lb of home-made explosives into Belfast's main commercial hub in the run-up to Christmas.
The detonator exploded but failed to trigger the rest of the device in a car park under the Victoria Square shopping centre.
Matt Baggott said: "The philosophy of these groups is simply hatred."
The bomb was in a barrel or keg in the back of a silver Renault Laguna.
The driver was stopped in the republican Ardoyne district by three masked men wearing boilersuits who ordered him to take the car to the car park. After abandoning the vehicle, he ran across the street to the nearby Musgrave Street police station and raised the alarm.
The Laganside court complex and dozens of shops and offices are situated nearby.
The chief constable added: "There has been a surge recently in dissident republican activity.
"We have seen letter bombs, under-car booby traps, blast bombs, hijackings.
"These groupings are trying to bring themselves to notice again. They seem to be in some form of bizarre competition to make sure that they have a profile."
Mr Baggott promised extra police patrols but said there would be no going back to the past and no "ring of steel" like that seen during Northern Ireland's 30-year conflict.
Assistant chief constable Drew Harris said the partial explosion shortly after 11pm last night caused damage to the car but none beyond the vehicle, which is being forensically examined.
"This was a terrifying experience for that poor driver because as he was going along obviously the device is situated right behind him and he is driving along with a live device which if it had detonated, even partially, would have caused him severe injury and even death," he said.
"A full explosion would have killed him outright. It is a reckless thing to plant such a large device in the city centre.
"We are viewing this as an effort to try and really disrupt the city centre in the run-up to Christmas.
"It is many years since we have had such a direct attack in the city centre of such scale, we are asking people to be vigilant. People will see an increased police presence in the city centre."