The device was found on the Antrim Road Police believe dissident republicans are behind a suspected “large improvised explosive device” found on north Belfast’s Antrim Road.
An alert started after calls claiming to be from dissident republican group Oglaigh na heireann.
Police said they cannot confirm yet if the device is a real bomb or a hoax.
The road has been closed since 1600 GMT on Tuesday and is likely to remain so until this evening. Up to 100 homes and businesses have been evacuated.
The alert is close to Antrim Road police station.
Army bomb disposal experts are still examining the device and have carried out cntrolled explosions on a suspect car.
PSNI Chief Superintendent Mark Hamilton said: “There’s no way I’m going to be opening the road again until I’m sure that there’s no risk of death or injury to anybody living or working in that area of the Antrim Road.
“We’ve received a number of calls over a 24-hour period and the last one in particular led us to believe we were looking for an unexploded bomb in an unstable condition.”
Ch Supt Hamilton said 40 to 50 families had been moved from their homes, while a children’s home had also been evacuated and people under sedation in a clinic had had to be moved.
He said dissident republicans were likely to be responsible.
“The people we’re dealing with want to wreck this community – they live in this community but they want to wreck it. They want to kill people in the community, they want to kill police officers,” he said.
“If this turns out to be a real device, its madness, because it will have been lying there and hundreds of people will have walked past it.”
‘Disruptive’
Some families who were moved from their homes were put up at Fortwilliam and McCrory Presbyterian Church overnight.
Reverend Lesley Carroll said the alert had been “very disruptive”.
Sinn Fein MLA Gerry Kelly said police had received three coded warnings. But he said the calls were very confusing.
“They said there was a bomb within the distance of some mile along the Antrim Road. That was checked out,” Mr Kelly said.
“In a second phone call, they said it was somewhere on the Antrim Road and in the third phone call it has been narrowed down to somewhere around the Glandore area.
“They said in their latest phone call it was in a dangerous condition. We need to know where that is so that something can be done about it.”
This article is from the BBC News website. © British Broadcasting Corporation, The BBC is not responsible for the content of external internet sites.