The four-member Independent Monitoring Commission (IMC) identified the splinter groups as Óglaigh na hÉireann and Saoirse na hÉireann.
The IMC said Óglaigh na hÉireann, a breakaway faction from the Continuity IRA, was responsible for one assault and a robbery at a post office in the period between September 1 and November 30 last year.
It also tried to recruit members of the Real IRA.
Saoirse na hÉireann was described as a group of disaffected, mostly young, republicans, the majority of whom are based in Belfast.
The organisation also claimed responsibility for two hoax bombs in September.
The commissioners said: “It remains to be seen how and to what extent these new groupings develop. Previous experience with splinter dissident groupings indicates that they might not necessarily be long-lasting. We will include any further information in future reports.”
The IMC said it was difficult to attribute some dissident republican activity during the period to specific groups.
The incidents included the planting of a viable bomb at Belfast City Hall at the end of November and two hoaxes at the home of a senior member of the nationalist SDLP.
The commission also noted two hoax bomb alerts in October and one the following month.
The report speculated that hardline republicans were using the bomb scares to study how the security forces reacted in such circumstances and help those responsible plan future attacks.
The IMC said the Continuity IRA remained a threat and was training members, continuing efforts to recruit new members, developing its equipment and seeking to acquire munitions.
The organisation was responsible for a hoax device under a Royal Irish Regiment officer’s car and planned a campaign of viable and hoax bombs against private, commercial and military targets.
“We think it probable that the organisation was responsible for planting four explosive devices in the period under review, one against an Orange Hall and for hoaxes at commercial premises and the Down Royal racecourse,” the report said.
“It instructed some members of Óglaigh na hÉireann, the new grouping which has splintered from CIRA, to leave Northern Ireland.”