Bristol Mayor Marvin Rees has called for calm after the grave of an African slave was vandalised in an apparent "retaliation attack".
It follows the toppling of the statue of slave trader Edward Colston during a Black Lives Matter protest in the city centre.
The Grade II listed headstone and footstone at St Mary the Virgin in Henbury were smashed on Tuesday 16 June.
A message was also found scrawled in chalk on flagstones nearby, calling for the Colston statue to be put back or "things will really heat up".
They graves pays tribute to 18-year-old Scipio Africanus, who died in 1720.
He was a servant in the household of the Earl of Suffolk, who lived in the Great House in Henbury, and who paid for the ornate memorial.
The gravestones feature black cherubs and an inscription referring to Scipio's conversion to Christianity. They have now been covered in plastic to protect them.
Avon and Somerset Police is now investigating the incident.
A spokesperson for the force said: "We believe the incident occurred between 12pm on Tuesday June 16 and 8am on Wednesday June 17.
"Our investigation into what happened is at an early stage. Officers have been at the scene and have carried out house-to-house and CCTV inquiries."
Marvin Rees said the grave is an "iconic piece of Bristol's history."
He also called for an end to racially-motivated attacks, saying, "We don’t want to go down this tit-for-tat invisible attacks on each other".
In a statement following the damage, Bristol Diocese said:
Conservative councillor Mark Weston, who represents Henbury and Brentry, posted photos of the damage on Facebook and described it as a "retaliation attack for the recent events involving the Colston statue."
He continued, "I am deeply saddened by what is happening. We have seen war memorials defaced and statues vandalised and I have to wonder where this will end."
A fundraising page has since been set up to help restore the headstones and has currently raised more than £2,000.