The UN Security Council has slapped sanctions on M23 rebels in the Democratic Republic of the Congo and their alleged Rwandan allies the FDLR, diplomats said Monday.

The move freezes the assets of entities or individuals linked to the groups and bars them from travel.We believe these designations will directly help advance the goal of a sustainable peace in eastern DRC," US Ambassador to the UN Susan Rice said in a statement.

"We urge the rank and file of both the M23 and the FDLR to defect and demobilize in order to disassociate themselves from the sanctioned groups."The decision came just hours before Rwanda was set to join the council as a non-permanent member on Tuesday for two years.UN experts accuse DR Congo neighbors Rwanda and Uganda of backing the M23, an accusation the two countries deny.

The council had already issued targeted sanctions, the latest round at the end of November, against three M23 military leaders, but had yet to sanction the entire group.DR Congo military officials allege that the M23 have formed an alliance with the Democratic Forces for the Liberation of Rwanda in a bid to gain more territory in the region.

The M23 was formed in April by former fighters in the National Congress for the Defense of the People, an ethnic Tutsi rebel group that was integrated into the army under a 2009 peace deal whose terms the mutineers claim were never fully implemented.

The FDLR's members are ethnic Hutus who were soldiers in the Rwandan army before being forced out of the country in the wake of the 1994 genocide, which killed 800,000 people -- mostly Tutsis.