TOKYO (AFP) - A Tokyo man accused of accessing a woman's Facebook account and allegedly downloading pictures of her in her underwear has been arrested, police and reports said on Tuesday (Nov 10).

In what is being reported as the first such arrest in Japan, Ryosuke Koga, 25, allegedly logged into the victim's Facebook account 17 times between January and March, a Tokyo Metropolitan Police spokesman said.

Investigators had also found that the IT firm employee allegedly kept approximately 770 Facebook and iCloud IDs and were investigating how he obtained the information, according to local media, including Jiji Press.

Koga could face up to three years in prison or a fine of up to 1 million yen (S$11,524), the police spokesman said, without providing further details.

Police were trying to establish how he acquired the login IDs of so many people, the mass-circulation Mainichi newspaper reported.

Koga downloaded pictures of the woman in her underwear, Kyodo News said, citing unnamed police sources. The police spokesman, however, did not confirm that report.

Tokyo police raided Koga's house after finding sexual images posted on the Internet in July last year, when they found the collection of ID data and passwords, the Mainichi said.