Police in Northern Ireland today appealed for information about an "indiscriminate and reckless" attack in which an explosive was hurled at officers in Belfast.
Three police officers were hurt in last night's incident and one remains in hospital with severe injuries to his arm which will require further surgery today.
Chief Superintendent Alan Todd, of the Police Service of Northern Ireland, described the incident as "a clear attempt to murder officers" and said it could have resulted in "mass murder" of members of the public walking outside shops nearby.
A number of uniformed police and detectives were investigating a robbery at a bookmakers in Shaw's Road at around 9pm when a man rode up on a bicycle and threw an explosive device at them, said Supt Todd.
The device exploded on the ground, and flying debris hit the officers and narrowly missed members of the public. Three officers were taken to hospital, two of whom were released shortly afterwards.
Supt Todd told BBC Radio 4's Today programme: "The other officer was treated last night for severe injuries to an arm. Those injuries will require further surgery today.
"This was a clear attempt to murder officers. This could have been a mass murder investigation this morning, not only of officers at the scene but indeed the members of that community who were going about their normal business on what is a shopping street.
"This was an indiscriminate and reckless attack aimed at killing police officers but with complete disregard to what might have happened to members of that community."
Supt Todd said that the nature of the explosive device and the motive for the attack were not yet known.
"We don't believe it is connected to the robbery at this stage, although it is early days in the inquiry and that can't be ruled out," he said.
"As to the motive, given that the people responsible haven't come forward and explained to anybody what their objective is and why they think this serves anybody's needs, that wouldn't be for me to comment.
"What is clear is that the people responsible have complete disregard for the local people in the area and the wishes of the wider public."