NHK has learned that a Japanese national, who is believed to have been a "volunteer fighter" with the Ukrainian forces, has died in Ukraine.

Sources close to the Japanese government say that a man in his 20s died in Ukraine on Wednesday. Details, such as where he died, are unclear.

The sources say this is the first time a Japanese national involved in Russia's invasion of Ukraine has died.

The Japanese embassy in Ukraine is now contacting the man's family in Japan.

The Japanese government had asked the Ukrainian government to verify a report about the death of a Japanese national through its embassy in Ukraine.

Japan's top government spokesperson said on Thursday that officials were checking the validity of information posted on social media about the man's death.

A Japanese government advisory urging all its citizens to evacuate from Ukraine is in place. And the government has been advising Japanese nationals not to travel to the country for any reason.