TOKYO - The presidential election of ruling Democratic Party of Japan (DPJ) started here Friday noon.

Prime Minister and incumbent party leader Yoshihiko Noda, 55, is facing challenges from three other candidates including former Internal Affairs Minister Kazuhiro Haraguchi, former Agriculture Minister Hirotaka Akamatsu, and another ex-Agriculture Minister Michihiko Kano.

With the support of many lawmakers and rank-and-file party members, Noda is set to retain the leadership and get re-elected, easily beating the other hopefuls in the contest.

Japan's Prime Minister Yoshihiko Noda attends Japan's ruling Democratic Party of Japan (DPJ) leadership election in Tokyo, Sept 21, 2012. [Photo/Agencies]