Vandalism of the stonework (Picture: Commonwealth War Graves Commission).
Graffiti has been sprayed onto stonework at the Portsmouth Naval Memorial.
It comes just days after commemorations at Southsea Common to mark 75 years since the D-Day landings.
The Commonwealth War Graves Commission (CWGC) only recently completed renovation works to the area in advance of the anniversary.
The names of more than 24,000 missing naval personnel of the world wars are listed on the stonework, but none of the name panels have been directly affected.
The CWGC said: "Whenever any such vandalism takes place we receive many thousands of well-wishes that far outweigh the negativity of a very small minority."
Meanwhile, a D-Day veterans' bench has been vandalised with Swastikas spray-painted onto it in Lincolnshire.
The incidents come less than a week after war graves were smashed in Bradford.