Loyalists have targeted the republican plot in Milltown Cemetery in a graffiti attack.
Spray paint was used to deface an engraved copy of the Proclamation and other stone work at the heart of the memorial in the west Belfast graveyard on Sunday night.
Sinn Fein MP Paul Maskey described it as a sectarian attack.
“All graveyards are sacred places and should be respected,” he said. “This attack is outrageous and does nothing other than cause distress to families whose loved ones are buried in the plot.
“I would like to commend the National Graves Association who tend to the republican plot and whose members are already involved in a clean-up of the graves.”
Vandals sprayed “F**k the IRA” and “Ulster forever”, and also damaged headstones in the attack.
There are 77 republicans buried in the newer part of the plot, including hunger striker Bobby Sands and three IRA members killed by the SAS in Gibraltar in 1988.
Within 48 hours, there was an apparent ‘tit-for-tat’ attack on a British Army war memorial in loyalist Woodvale Park, where IRA graffiti was sprayed on a unionist monument.
Deputy First Minister Martin McGuinness said that attack was “shameful” and as bad as the first.
“[It] is as repugnant as the attack on the republican memorial in Milltown Cemetery,” he said.