A man set himself on fire in central Tokyo in protest at a proposed law which could allow Japan to deploy its military overseas.
The man was taken to hospital after being hosed down but his condition was not immediately known, officials said.
Japan’s government could make the change to its pacifist constitution as early as next Tuesday.
The US-drafted constitution bans war and “the threat or use of force” to settle international disputes.
Witnesses said the middle-aged man, wearing a suit and tie, climbed onto a pedestrian bridge at Tokyo’s Shinjuku station.