Archaeologists believe they may have uncovered a secret stone dating back to medieval times in a Dundee graveyard.

The group, who are working at the Howff, think their latest discovery could be traced back to the 12th or 13th century.

Previously the oldest gravestone in the region was thought to be that of Thomas Muir in 1577. He was 54 when he died and was a Burgess of Dundee.

With the stone covered in moss and half-buried in the ground, permission from Historic Environment Scotland is required to have it removed for cleaning.

The Howff Preservation Society hopes to excavate the stone and find out who it belongs to.

Dr Oliver O'Grady, the archaeologist who discovered the stone, said: "It's been an absolute pleasure helping Simon and the group's dedicated team to map the Howff's important collection of burial monuments.

"Finding the medieval stone was an amazing added surprise and is a significant discovery for Dundee's archaeological heritage.

"It is a type known as a coped-stone and studying it should help uncover more about the Howff's hidden medieval past, so I'm really pleased for the group."

He added: "There are only around 90 examples of this type of medieval burial stone from Scotland.

"Dundee has a small collection at St Mary's church in the old town centre but this is a first for the Howff.

"The stone is currently in a poor condition so I am now supporting the group to find the best way to conserve and present the stone for future generations to enjoy."