Both outlets report that Holm's agent confirmed the news in a statement.
"It is with great sadness we can confirm that the actor Sir Ian Holm CBE passed away this morning at the age of 88," the statement read, in part.
USA Today reports that Holm had Parkinson's disease.
Holm played Bilbo Baggins in two of the Lord of the Rings films and in two films from the series' prequel trilogy, "The Hobbit."
Holm also appeared in the 1981 film "Chariots of Fire" and in the 1979 film "Alien."