Emperor Naruhito and Empress Masako on Tuesday laid flowers at a cenotaph in Ulaanbaatar for Japanese nationals who died in detention in Mongolia in the aftermath of World War II.
It is the first time that a Japanese emperor has mourned at a site where Japanese people were detained abroad, according to the Imperial Household Agency.
Before the cenotaph, which was built by the Japanese government, the emperor and empress bowed and observed a minute of silence under an umbrella as it was raining.
The imperial couple are on a visit to Mongolia from Sunday ahead of the 80th anniversary this August of the end of the war.
After the war ended, some 14,000 former Japanese soldiers and others captured by the former Soviet Union were transferred to Mongolia. About 1,700 of them died there.
On Tuesday, the emperor and empress were accompanied by Toshiei Mizuochi, 82, head of an association of families of Japanese war dead, and Fusae Suzuki, 88, whose father was among the Japanese detainees in Mongolia.
"I'm very grateful and honored," Suzuki told reporters. "Since the spotlight had not been on the detainees in Mongolia, I think their souls, including my father's, can now rest in peace."
Later on Tuesday, the imperial couple attended a banquet hosted by Mongolian President Ukhnaa Khurelsukh and his wife.
In a speech, Emperor Naruhito said that he hopes relations between the two countries will continue to develop, reaching "further heights toward the Mongolian sky."
The emperor thanked Mongolia for sending aid following the 1995 Great Hanshin Earthquake, the 2011 massive earthquake and tsunami in eastern Japan and the Noto Peninsula earthquake in 2024.
"The potential for exchanges and cooperation between the two countries is as vast as the Mongolian steppes," he said.
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