South Korea expressed "deep regret" Thursday over a ritual offering made by Japanese Prime Minister Shinzo Abe at the controversial Yasukuni shrine, which is condemned here as a symbol of Japan's past imperialism.

"Our government cannot help but express deep concerns and regret over Prime Minister Abe's offering to the Yasukuni shrine that glorifies its past wars of aggression and honors war criminals," Foreign Minister Spokesman Cho Tai-young said in a briefing.

"I once again call on Japanese politicians to try to build up trust from the international community on the basis of humble reflection on its history," Cho added.

Abe reportedly sent a "masakaki" tree, used in Shinto rituals, earlier on Thursday to the Tokyo shrine as the country begins its annual autumn festival. The prime minister, however, skipped a visit, possibly to avoid backlash.

Whether he would pay a visit to the shrine was closely watched as such actions by Japan's leaders have frequently prompted strong condemnations its from neighbors including South Korea and China.

The Yasukuni shrine, which honors many convicted Class A war criminals along with millions of Japanese war dead, is viewed here as symbolizing Japan's imperial past.  

Relations between the two neighbors have been unusually icy of late, with Seoul condemning the Abe administration's repeated nationalistic remarks and inaction over addressing the issue of Japan's sexual enslavement of South Korean women during World War II. (Yonhap News)