Proxy advisers oppose 3 Axcelis board directors

SAN FRANCISCO, April 18 (Reuters) - Proxy advisory firms Riskmetrics and Glass Lewis on Friday recommended that shareholders of Axcelis Technologies Inc (ACLS.O) withhold votes to oppose election of three directors at an upcoming annual meeting.

Axcelis's corporate bylaws say that any nominee who has a greater number of votes withheld than voted in support must offer to resign. The board currently has seven directors.

Axcelis is trying to fend off a $615.6 million takeover bid from Japan's Sumitomo Heavy Industries (6302.T). (Reporting by Anupreeta Das; Editing by Gary Hill)