Pro-Chinese supporters and protesters kicked and punched one another on Saturday during the Olympic torch relay, in incidents that injured at least four Chinese, officials said.
A demonstrator, whose nationality was unclear, kicked at the pro-Chinese crowd and Chinese supporters charged with flagpoles until Japanese police broke up the clash near the main train station here, an AFP photographer said.
One young man, who appeared to be Chinese, was seen on the ground with bloody cuts on his forehead as supporters wrapped a Chinese flag around him.
It was one of the most serious of a string of incidents throughout Japan's leg of the worldwide relay in the central mountain town.
Chinese students, who outnumbered protesters, were seen surrounding the demonstrators who waved Tibetan flags, including at the relay's final point.
At least four Chinese people were injured in clashes, including one who was taken to a hospital for cuts to his forehead, according to police and fire department officials. None of the injuries were considered serious.
Two protesters were arrested for bursting onto the street in attempts to disrupt the relay. Police said one was Japanese and the other from another Asian country.
The non-Japanese man who was arrested was heard screaming at the top of his lungs in English, "Free Tibet!", as police tackled him down and carried him away.
Demonstrators also threw trash, an egg and flares towards the torch at different points, briefly holding up the relay. No arrests were reported in those incidents.
More than 3,000 police were deployed in Nagano, the site of the 1998 Winter Olympics, which has raised security to a level usually accorded to Emperor Akihito.