Dark animated norse saga. Early 2000s?

I have a memory of seeing a 2D animated film based on norse/icelandic sagas at an arts cinema as a child. It was quite dark and violent in tone and not really made for children. The scene I remember most was an ambush where warriors hid in sacks hanging in the great hall, but they were double crossed and beaten to death while hanging in the sacks.

This would have been in the early 2000s, and it was definitely too adult for my age then! I have a feeling it may have been a foreign (scandinavian?) film with subtitles, but I’m not entirely sure. As it was shown at an arts theatre, it might be quite a niche production.

Would love to find out what it was, as I’ve been searching for years!