The shooting of a top gangland boss in Japan has sparked fears of a turf war between rival gangs in Tokyo.
The gang boss was shot dead in his car
Two members of the Sumiyoshi-kai gang were arrested by police on suspicion of involvement in revenge attacks.
The killing of a senior member of the gang on Monday was followed by a spate of shootings at the Tokyo headquarters of a rival gang.
The gun violence has caused alarm among residents in Tokyo, where such incidents are rare.
The violence began with the fatal shooting of Ryoichi Sugiura, 43, in his car in Tokyo on Monday.
Within hours, the offices of the Yamaguchi-gumi - Japan's largest crime gang, which originated in Kobe - had been fired upon.
Shooting into the doors and windows of a rival gang's offices are the hallmark of underworld retaliation in Japan, the Associated Press reports.
Japanese police arrested two members of the Tokyo-based Sumiyoshi-kai and reportedly raided their offices in a bid to try and halt the escalating violence.
Violence between the Yamaguchi-gumi gang and the smaller Sumiyoshi-kai is not uncommon.
The rivalry is believed to stem from Yamaguchi-gumi's expansion from Kobe into Tokyo, which is Sumiyoshi-kai's traditional base.
The number of gangsters - known as yakuza - in Japan has grown in the past 10 years to more than 85,000, according to official figures.
Police have tried to crack down on yakuza, putting pressure on their illegal activities, such as drug-trafficking, gambling and prostitution.