The Osaka police have found the severed head of a missing woman at a lodging facility - Representational Image Issei Kato/ Reuters

The Osaka police in Japan have found the severed head of a missing woman at a lodging facility on Saturday (24 February) after she was last seen with an American man.

According to the Hyogo Prefectural police the severed head found in a suitcase, belongs to a 27-year-old woman from Sanda, Hyogo Prefecture.

The woman's mother contacted the police after she said she could not reach her daughter. Her complaint sparked a police investigation.

The unnamed woman was last seen walking with an American man who was arrested on Thursday, The Star reported.

The man was arrested for allegedly "confining" the woman in an apartment in Osaka, the Japan Times reported.

Security footage showed the man walking into the apartment building with the woman on 16 February. However, the woman was never seen leaving the building, the Japan Times reported.

The man was caught on surveillance camera coming in and out of the building alone several times, carrying a large bag, local media reported.

The man has reportedly denied all the allegations against him.

According to initial reports, the woman had told her friends that she was going to Osaka to meet a man she had met on an app.

Before she went missing, the woman had posted on Instagram that she was going to "meet Jay," an apparent reference to the American.

The man is said to have arrived in Osaka as a tourist in January, The Star reported.

The search for other body parts is on, police said.