It depends on the definition of the medieval town/ urban space to a certain degree - the very classic study of medieval towns, focusing on its distinct legal and governmental body like that of Henri Pirenne would not certainly admit that there were towns in Vikiing Age Scandinavia, but as I summarized before in: In what ways were pre-Viking Scandinavians (6th, 7th, 8th centuries) culturally distinct from their 9th century descendants? In the areas of language, religion, economics, military tactics, technology, social structure, etc, a few "trading place" with planned land quarters and somewhat dense settlements including craftspeople like blacksmiths had already been established around the North Sea in course of the 8th century CE.
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Biographer Rimbert narrates that Frankish missionary Ansgar (Anskar) worked and built the earliest church in collaboration with the local Scandinavian ruler (governor?) in two of such "trading places", namely Birka in the Mälaren (Central Sweden, west to Stockholm) and Ribe in western Denmark. They had already been "urbanized" by the beginning of the 9th century, so Ansgar the missionary primarily preached town dwellers there, not to rural Scandinavian farmers in the countryside.
Norway also had a Kaupang (Skiringssal) in Vestfold, though its 1st mention in written source dates only backs to the end of the 9th century (now archaeological excavation confirms its older provenance).
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