Ezekiel 613 Then shall ye know that I am the Lord, when their slain men shall be among their idols round about their altars, upon every high hill, in all the tops of the mountains, and under every green tree, and under every thick oak, the place where they did offer sweet savour to all their idols.
The Celts Nora Chadwick p. 146
Julius Caesar, in his work on the Gallic Wars, describes Druids sacrificing humans to the gods.
In one memorable account, he describes,
Druids in white robes, having people placed in giant straw figures. These 'wicker men' were set on fire and those inside all burned to death. This was done to win the favor of the gods.
There are some who claim that accounts of Druids conducting human sacrifices are merely Roman propaganda.