Alleged killer Borce Ristevski has been bashed on his first day in prison after being charged with the murder of his wife, Karen.

Multiple sources confirmed the 53-year-old was assaulted while he was in the yard of the Melbourne Assessment Prison yesterday afternoon.

It is understood the bashing was not severe, and was described as a "welcome" by one source.

A Corrections Victoria spokeswoman said a 53-year-old prisoner was treated for minor injuries.