A military-style hand grenade was thrown at a police patrol in east Belfast.
The device was hurled at officers in the republican Short Strand area on Friday night.
Police Service of Northern Ireland (PSNI) Chief Constable George Hamilton branded the incident an "act of madness".
He tweeted: "Device thrown at local police in Short Strand last night was an act of madness that could have killed or injured police or local residents."
The security operation in the Short Strand area is continuing and Short Strand remains closed to traffic, the PSNI said.
Police officers were responding to reports from local residents of anti-social behaviour in the vicinity of the Short Strand area when the device was thrown at around 10.15pm in the vicinity of Pottingers Quay.
The device failed to explode, none of the police officers were injured and no damage was caused.
A number of residents were evacuated from their homes amid the security alert that followed the suspected attack.
The finger of suspicion will again fall on dissident republicans opposed to the peace process.
T/Superintendent Bobby Singleton, of Belfast City policing district, said: "Those who carried out this attack showed a total disregard for the safety of the local community and worryingly, for the second time in as many days, young people who were in the vicinity at the time of the attack.
"It is only by sheer good fortune that we do not have a fatality on our hands as this attack occurred in a built-up residential area. Police officers join to serve our communities and work tirelessly to keep them safe.
"In contrast to the irresponsible actions of those behind the attack, the officers targeted insisted on remaining at the scene to assist in keeping local residents and their colleagues safe.
"This is the second attempt by terrorists to kill people in Belfast in 48 hours. Thankfully, on both occasions they failed but I would appeal to people to remain vigilant and appeal to everyone in the community to continue to work with police by providing information to us so we can keep everyone safe."
The incident on Friday came the day after a suspected undercar booby trap bomb was found on a street in north Belfast.
The viable explosive device was apparently kicked by a young boy while it lay on the ground in Linden Gardens, off the Cliftonville Road.
Detectives are investigating whether the bomb had fallen off a car belonging to someone with a connection to the armed forces. Dissidents were again blamed for that incident.