TOKYO — Japan’s conservative Liberal Democratic Party returned to power in a landslide election victory Sunday after three years in opposition, according to unofficial results, signaling a rightward shift in the government that could further heighten tensions with China, a key economic partner as well as rival.

The win means the hawkish former Prime Minister Shinzo Abe will get a second chance to lead the nation after a one-year stint in 2006-2007. He would be Japan’s seventh prime minister in 6½ years.