The British army has carried out a controlled explosion at the Republican Plot in Milltown Cemetary.
Army Technical Officers were sent to the west Belfast graveyard after a suspicious object was discovered. It was later declared a hoax by police.
The plot - containing the grave of IRA hunger striker Bobby Sands - was damaged in an overnight attack by vandals.
Sinn Féin confirmed that 16 graves in the Republican Plot, which contains the graves of hunger strikers and three Provisionals killed by the SAS in Gibraltar, were desecrated.
Headstones were smashed and flowers laid by the families were scattered around the recently refurbished memorial.
West Belfast councillor Mr Michael Browne said relatives were "extremely distressed". He said: "This is not simply a Republican memorial, it is the actual graves of many IRA volunteers and Sinn Féin activists killed over the past 30 years.
"The monument was recently refurbished through the voluntary work of Belfast republicans. Republicans throughout the city will be angered at this turn of events and I am sure they will rally to the aid of the National Graves Association as they seek to rebuild the monument.
"Those responsible for this attack are beyond contempt and they need to reflect long and hard upon their actions."
The graves have been vandalised in the past. In January 2000 more than 20 granite memorial plaques were damaged, some beyond repair.