A man threw a Molotov cocktail Wednesday evening at the Foreign Ministry building in Tokyo and then apparently tried to commit hara-kiri before being taken into custody, a ministry guard and police said.

When apprehended, the man reportedly grumbled to police: "A Japanese was beaten by a Chinese at Yasukuni Shrine."

No one else was hurt in the attack, which did not cause serious damage, and the fire was extinguished, the guard told reporters, adding that the man appeared to be in his late 20s and had climbed over a fence to enter the ministry before throwing the firebomb near the main entrance.

The man then stabbed himself in the abdomen with a 20-cm kitchen knife, the guard said.

The man was taken to hospital and remains conscious.

The motive for the incident, which occurred at around 6:40 p.m., is still unknown and police said they are trying to confirm the man's identity.