Google said on Monday that Arthur Levinson had resigned from its board following increased regulatory scrutiny over his membership as a director of both the top Internet search company and Apple Inc.

The resignation by Levinson, the former chief executive of Genentech and a Google board member since 2004, comes about two months after Google CEO Eric Schmidt quit the board of the maker of Mac computers and iPhones.

Google and Apple, long seen as allies against Microsoft Corp's tech dominance, increasingly find themselves competing on a number of fronts, including operating systems and the fast-growing smartphone market.

At the time, Schmidt's resignation was seen as helping defuse some scrutiny of the companies' relationship, but the U.S. Federal Trade Commission has continued to investigate the relationship between the two boards.

Levinson left Google despite Schmidt's urging earlier this month that he stay.

Art has been a key part of Google's success these past five years, offering unvarnished advice and vital counsel on every big issue and opportunity Google has faced, Schmidt said in a statement on Monday. Though he leaves as a member of our Board, Art will always have a special place at Google.

Shares of Apple and Google marked narrow gains in early trading. Google rose 1.5 percent to $524.00, while Apple climbed 0.5 percent to $191.45.

(Reporting by Franklin Paul; Editing by Lisa Von Ahn)