TOKYO — Shinzo Abe took office as Japan’s seventh prime minister in six years Wednesday and vowed to overcome the deep-rooted economic and diplomatic crises facing his country.

Abe was elected as Japan’s leader hours earlier Wednesday, bringing back to power the conservative, pro-business Liberal Democratic Party that governed for most of the post-World War II era. It replaces the liberal-leaning government of the Democratic Party of Japan that lasted three years.