The Fragmentary Annals of Ireland record an instance of a band of Norwegians led by the sons of Rognvald Eysteinsson (or possibly Ragnarr Loðbrók) heading south from the Orkneys and raiding and plundering through Iberia, probably taking some slaves in the process.

Afterwards, the brothers crossed into Africa (possibly Northern or Western Africa) and fought two battles against the "Mauritanians", wounding their king and forcing them to flee despite suffering heavy casualties. The Norwegians then plundered the land of the "Mauritanians" and:

swept across the country, and they devastated and burned the whole land. Then they brought a great host of them captive with them to Ireland, i.e. those are the black men. For Mauri is the same as nigri; 'Mauritania' is the same as nigritudo. Hardly one in three of the Norwegians escaped, between those who were slain, and those who drowned in the Gaditanian Straits. Now those black men remained in Ireland for a long time.

The geographical clues indicate that they probably landed in North Africa, meaning that those 'black men' would have been Muslims. On the other hand, the terminology used probably tells us that the men the Norwegians fought against were black sub-Saharan Africans; fir ghorma (lit. 'blue men') implies a very dark complexion, and survives in Modern Irish as the word for 'black person'.

There are other textual examples of Scandinavians based in Ireland raiding and probably slaving in Muslim Iberia; in one notable example, a Muslim ruler supposedly sent an embassy to Ireland to discuss with the Norwegians who just raided his realm, and was surprised to find the island inhabited by a completely different people!