A military grenade thrown at police in the North landed at the feet of two young children, a senior officer said.
The device did not explode but if it had it is “highly probable” it would have killed the two boys and an officer they were talking to, according to Chief Superintendent Stephen Martin.
The incident happened in the Creggan area of Derry yesterday evening as police responded to a hoax bomb alert in the area.
“That grenade landed at the feet of one police officer and there were three other police officers in close proximity to that,” said the Police Service of Northern Ireland (PSNI) commander.
“Alarmingly, two young boys under the age of 10 had pedalled their bicycles up and were talking to the police officer when the device fell at his feet.”
He added: “This was a military grenade, this was not an improvised grenade, these are designed for warfare, these are designed as anti-personnel weapons to kill people.
“If that had exploded in that environment we were faced with last night I think it is highly probable that I would be talking today about fatal injuries to both a police officer and to two young boys.”
Police believe dissident republicans opposed to the peace process were responsible for the failed attack.
Two officers chased after the man who threw the grenade but he escaped through alleyways around the Kildrum Gardens area.
Police are not yet sure whether the hoax device they had been examining was left on the nationalist estate as a lure or if the attack was opportunist.
Mr Martin pointed out that officers had been in the area for a number of hours before the incident occurred.
“I am counting my blessings today, as are the community in Derry, that that device did not detonate, but I am sure the person who threw it believed it was going to detonate and that person was intent on killing police officers,” he said.
He said he was heartened by condemnation from across the political spectrum.
“I am encouraged. I know that these misguided individuals are small in number and I know that the overwhelming majority of the people in Derry and indeed throughout Northern Ireland support the police.”
Mr Martin declined to be drawn on questions about the origin and age of the grenade.
The attack comes five weeks after a dissident republican booby- trap car bomb killed PSNI constable Ronan Kerr in Omagh.
A grenade was also thrown at officers in west Belfast last November. It exploded, injuring three of them.
“We have seen in recent weeks some of these do explode and some do not,” said Mr Martin.
“Last night we were lucky. Today, I am lucky that I am not talking about the serious injury or fatal injuries to a police officer or police officers and also I am not talking about serious injuries or fatal injuries to two young boys under the age of 10.”