A new investigation into the garments - found in 9th and 10th Century graves - has thrown up groundbreaking insights into contact between the Viking and Muslim worlds.

Patterns woven with silk and silver thread have been found to spell the words "Allah" and "Ali".

Two years ago, researchers re-examined a silver ring from a female tomb at Birka and found the phrase "for Allah" inscribed on the stone.

The text was Kufic, developed in the Iraqi town of Kufah in the 7th Century - one of the first Arabic scripts used to write down the Koran. (BBC)