The areas of Northern and Western Estonia belonged in the Scandinavian cultural sphere during the Viking Age. Estonia was not a unified country during the Viking Age, and the area of Ancient Estonia was divided among loosely allied regions. The Viking Age in Estonia is often considered to be part of the Iron Age period which started around 400 AD and ended around 1200 AD, soon after Estonian Vikings were recorded in the "Eric Chronicle" to have sacked Sigtuna in 1187.