Police have said they believe a large pipe bomb which was found close to a school in west Belfast may have been thrown at them overnight.
They said dissident republicans were suspected of being behind the device on the Glen Road.
St Teresa's Primary School was closed and a number of homes were evacuated after it was found early on Tuesday morning.
It was found while emergency services dealt with a fire at a Spar shop.
Police said another line of inquiry was the fire had been started to lure police officers to the area.
Ch Supt Mark Hamilton said it was thanks to the "close observations" of a police officer that the pipe bomb had been discovered and that the "finger of suspicion" pointed towards dissident republicans.
"We are trying to establish whether or not it is connected to the fire," he added.
"We are continuing to examine the circumstances of the fire to see if it was deliberate or not.
"The worrying thing is that people would try and attack us in this way, but secondly it did not detonate initially and it was only by the close observations of a good police officer that we found it.
"If we had not found it, it would have lain there this morning.
"It is directly opposite a primary school and the chances are the first people to have come across it would have been families coming to school this morning.
"I have had discussions with the Army bomb squad and this could have had horrendous consequences if someone had picked it up."
Mr Hamilton said the device was found on the footpath in front of the Spar shop after the fire service attended the blaze there at 03:00 GMT.
Mr Hamilton added that the device which had the capacity "to kill or maim" had been taken away for further examination.
He said it was "particularly chilling" given the fact that a primary school was so close to the scene.
"This is a residential area and we could have been looking at serious tragedy here," he said.
"There is absolutely no doubt that this device was intended to murder and we would ask anyone with any information in relation to this incident to come forward and tell us what they know about this."
Police thanked local residents for their patience while the Army dealt with the device.
They said the Glen Road had now reopened and that residents had been allowed back in their homes.