A Chinese arson suspect who was released from a Seoul prison after the court decided not to extradite him to Japan, left for home Friday, according to multiple Seoul sources.

The South Korean court on Thursday rejected Japan's request to hand over Liu Qiang, 38, to be prosecuted for an alleged arson attack in 2011 at a controversial World War II shrine in Tokyo, saying that the crime he had committed was politically motivated.

Liu departed for Shanghai, China on a 8:55 a.m. flight through Incheon International Airport, South Korea's main gateway west of Seoul, sources said.

Japan in May of last year asked South Korea to hand over Liu, who had served a 10-month prison term in Seoul for a separate attack at the Japanese embassy in South Korea earlier last year.

The South Korean court proceedings were closely watched since Beijing also asked Seoul to allow him to return home, arguing that the alleged arson attack in Tokyo was not personally motivated.

Amid the diplomatic foray, Seoul decided to resolve the dispute through a court ruling. South Korea has extradition treaties with both China and Japan.

After the court ruling, Japan lodged a protest against South Korea's foreign ministry and demanded that Seoul hand over Liu by faithfully implementing an extradition treaty with Japan, a Japanese embassy official in Seoul told Yonhap News Agency late Thursday. He asked not to be identified, citing the issue's sensitivity.

China, meanwhile, "welcomed the result," Foreign Ministry Spokesperson Hua Chunying said.

The Chinese man fled to South Korea after allegedly launching the arson attack in Tokyo in December 2011. In Seoul, he made the Japanese Embassy his next target and hurled firebombs into the compound.

He was arrested at the scene and subsequently sentenced to 10 months in prison. He testified in court that he was angry at Japan because it continues to refuse to apologize for its wartime atrocities. He said his grandmother was one of the many Asian women forced by Japan to serve as sex slaves for its front-line soldiers.

Liu also testified that his grandfather worked with Xi Zhongxun, father of China's new top leader Xi Jinping, in a guerrilla campaign against Japanese occupational forces in the early 20th century, according to court documents.

South Korea kept Liu in detention pending the outcome of the extradition trial. (Yonhap News)