Firefighters in Japan are battling a blaze in mountains near Tokyo.

The fire started Tuesday night in Gunma Prefecture next to the Tokyo metropolitan area.

About 400 hectares of forest had burned and firefighters were still working to control the blaze as of 5pm local time.

The fire approached within about 1,000 feet of homes but first responders said there was no damage.

The area has been under an alert for dry weather conditions but the cause of the fire remains under investigation.