Fifty beheaded young men found in a burial pit in Weymouth last year were probably executed Vikings, archaeologists have revealed.

Teeth samples from 10 of the decapitated warriors discovered show that they were Scandinavian invaders who fell into the hands of Anglo-Saxons.

Dating back to between AD 910 and AD 1030, the mass war grave is among the largest examples ever found of executed foreigners buried in one spot. The remains were analysed by Jane Evans and Carolyn Chenery at NERC Isotope Geosciences Laboratory, part of the British Geological Survey, based in Nottingham.

The isotopes - variations of elements - found in the men's teeth show that they grew up in countries where the climate is colder than in Britain, with one individual thought to be from north of the Arctic Circle.

The unique burial site was uncovered on Ridgeway Hill in June 2009 during an earthwork operation for a relief road. Over the following two months, Oxford Archaeology carefully removed the 51 decapitated skulls from the ground - which were placed in one distinct area of the pit - and the bodies discarded haphazardly in another area of the pit.

It appears the men were slaughtered by local Anglo-Saxons at a designated formal spot, probably in front of an audience.

At the time the Anglo-Saxons were falling victim to increasing Viking raids, from a couple of ships up to invasion forces of 100 boats. The uneasy relationship between the two groups eventually ended with the country being ruled by a Danish king.

Oxford Archaeology project manager David Score said: "The find of the burial pit on Ridgeway was remarkable and got everyone working on site really excited.

"To find out that the young men executed were Vikings is a thrilling development.

"Any mass grave is a relatively rare find, but to find one on this scale, from this period of history, is extremely unusual and presents an incredible opportunity to learn more about what is happening in Dorset at this time."