Archaeologists are working to unravel the mystery of a six-headed burial of two 15th Century soldiers in the Highlands.

The remains of two men in their 40s were found on top of each other in a single coffin under Tarbat Old Parish Church in Portmahomack, Easter Ross.

But shocked experts at the site also discovered four other skulls in the grave which had been placed around the bodies in what has been described as a "special burial".

One of the men in the grave died from "horrific" sword injuries that removed the bottom half of his face with a second cut found above his left eye.

The second had injuries caused by a bladed weapon as well as blunt force.

Dr Cecily Spall, director of York-based Fieldwork Archaeological Services, said the remains - which were originally discovered in 1997 - were 'unlike anything that's been found in Scotland or anywhere else in Britain'.

The skeletal remains are thought to date from the 15th century when Clan Ross and Clan Mackay fought out a bloody rivalry in the area that arguably peaked with the Battle of Tarbat in the 1480s.

Then, Clan Ross cornered a raiding party of Clan Mackay, with many killed in the encounter.

Survivors of the attack sought sanctuary in the church, but the Rosses set fire to it, killing all those hiding inside.

According to Dr Spall, the men and skulls were buried in the most prominent part of the church, in the mouth of the crypt directly under the nave.

he said: "There were 88 burials from the medieval period but this one stood out.

"In the intervening years technology has advanced and we're now unpackaging it using new science.

"We excavated the site for 13 seasons. We don't know of anything quite like it.

"The fact that one man was buried with six skulls around his head is quite phenomenal.

"It's not like anything that's been found in Scotland or anywhere else in Britain.

"What we want to understand is the experience of these men. This warrior class could go out and fight for a wage.

"Some of them ended up in Scandinavia as mercenaries, for example.

"We think we understand Scottish identity, but here we have facts on the ground which will help us furnish a more realistic understanding of this time. That is why we are so excited about it."

More than 170 skeletons, including those of 40 children, have been found both under the church and in the graveyard, with the site spanning five key time periods.

It was first occupied during the sixth to seventh centuries when the land was used as a Pictish farmstead.

It then became an important Pictish monastery, which was destroyed around 800AD by a Viking raid, before the monastery was later replaced.

The archaeological team will now use advances in DNA analysis to determine when the men died, where they were from and whether they were related.

Dr Spall added: "The burials will be radiocarbon dated to see when they died and carbon isotopes will be used to see where they were born.

"We're also going to get them analysed to see if any ancient DNA exists to see whether they were related and we've had one of the faces reconstructed."

"At this time, burials were incredibly orthodox, so this deviates massively from what you would expect to find."

Dr Spall has been working at the Portmahomack site with Dr Shirley Curtis-Summers of the University of Bradford.

Dr Curtis-Summers, a specialist in human osteology, said: "The injuries suffered by the men suggest they were very, very seasoned fighters."