Outgoing Japanese Ambassador to China Hideo Tarumi expressed regret on Monday for failing to help realize the release of a senior Astellas Pharma employee whom Beijing authorities have detained since March over alleged spying activities.

The envoy, who met with the detained Japanese national for the first time last week, said at a news conference that he did so just before finishing his three-year tenure to "offer a personal apology" and convey that Tokyo will keep working to realize his early release.

The man in his 50s was formally arrested in October on suspicion of espionage. Prime Minister Fumio Kishida reiterated his call for the citizen's release during a November summit meeting with Chinese President Xi Jinping in San Francisco.