Police were surrounding a post office in Japan late Tuesday as a suspected gunman held at least one person hostage following an apparent shooting at a nearby hospital that wounded two people.

TV images showed the suspect, reported to possibly be in his 80s, inside the building with what looked like a gun attached to a cord around his neck in Warabi, outside Tokyo. 

His motive was unclear but police believe he was also involved in the incident at the hospital and media reports said that a fire in an apartment block may also be linked.

"At approximately 2:15 pm today (0515 GMT), a person took hostages and holed up at a post office in Chuo 5-chome area of Warabi city... The perpetrator is possessing what appears to be a gun," the city authorities said on their website.

"Citizens near the scene are urged to follow police instructions and evacuate in accordance with police instructions."

Television footage showed a woman in her 20s, believed to have been a hostage, walking out of the post office shortly before 7:30 pm. 

It was unclear how many people were still being held but earlier it was reported that a 30-year-old woman was inside.

Police were talking to the man by telephone, NTV reported.

The Yomiuri daily had reported earlier that around 10 post office staff may be inside the building and that the suspect may be carrying kerosene.

Several police cars with flashing lights were situated around the three-storey building as night fell, footage showed. 

"This is a quiet neighbourhood. I can't believe something like this is happening," local resident Tetsuo Sasaki, 70, told AFP.

"I used that post office just yesterday," said his wife Reiko Sasaki, 64. "I could have been at the wrong place at the wrong time. I could have been the target."

Hospital shooting

Earlier at a nearby hospital in Toda, two people were slightly wounded - reportedly a doctor and a patient - after shots were apparently fired from the street into the building.

Police "believe the man was at the hospital and came to the post office", a city official told AFP.

"After 1:00 pm, I heard a woman shouting 'Someone, please come,' and a nurse told me, 'Stay away from the windows and keep your head low,'" a man in his 60s who was inside the hospital told broadcaster NHK.

"Around 2:00 pm, I looked inside the doctor's office, and saw a pool of blood next to an examination table. I didn't hear a gunshot. But a nurse said she heard two gunshots," the man said.

Fuji TV said police were also investigating a possible link between the man and a fire at an apartment building in Toda earlier in the day. No one was injured in the fire, it said.

Violent crime is rare in Japan, in part because of strict regulations on gun ownership, but cases still occur.

Last year, former former prime minister Shinzo Abe was shot dead and this April a man hurled an explosive towards current Prime Minister Fumio Kishida. Kishida was unharmed.

The following month, a man holed up in a building after allegedly killing four people, including two police officers and an elderly woman, in a gun and knife attack.