The dissident republican group Republican Action Against Drugs (RAAD) is partly responsible for the increase in paramilitary-style attacks in Londonderry, according to the IMC.
In its latest report, the Independent Monitoring Commission referred to the "growth of vigilante organisations which claim to want to 'clean-up' (their term) anti-social behaviour".
The IMC said these groups - which included RAAD and the Belfast group, Concerned Families Against Drugs, were "a factor behind the increase in the number of attacks in some nationalist areas".
The body, which is responsible for monitoring paramilitary activity, also said it believed the groups had undertaken attacks which included the use of pipe bombs.
The report, which was released on Wednesday, follows the shooting of a man in the Creggan area of Derry on Tuesday night.
Tony Dalzell, 23, was shot in the legs five times at his home in Iniscarn Crescent as his 14-year-old sister and her friends were held at gunpoint.
Local residents have said they believe RAAD was responsible.
It is believed the group has been behind almost a dozen similar attacks in the city over the past year.
RAAD admitted an attack on a 27-year-old man, who was dragged from a house in the Brandywell by a masked gang and shot in the Bogside four weeks ago.
In May, the mother of a Derry man who died in Glasgow from a suspected drugs overdose blamed RAAD for his death.
Gary Cullen, 26, from Cornshell Fields, moved to Scotland two weeks after the organisation warned he would be shot if he did not leave.
After a similar paramilitary-style attack in Creggan in September, RAAD said it had "vowed to remove the scourge of drug dealing from within the local community".
PSNI Inspector Jon Burrows has promised to "take on" the group and dismantle them.
"Groups like RAAD and INLA that carry out these attacks play into the hands of drug dealers and rapists as officers can't be in two places at once."
"People have a choice to make," he added.
"Do we want police officers investigating the shootings or do they want us investigating burglaries?"