Athens marathon gold medalist Mizuki Noguchi ran the final leg of the relay, which saw only minor scuffles along the 18.7-kilometre (11.6-mile) route through the city that hosted the 1998 Winter Olympics.
Police guards in track suits surrounded the torch bearers and another 100 uniformed riot police ran alongside six patrol cars and two motorcycles. They were backed up by thousands of other police.
At the end of the relay at a Nagano park, Noguchi was greeted by a throng of Chinese supporters, far outnumbering the pro-Tibet demonstrators who were ushered to a hillside away from the celebrations.
Im so glad that I could safely light up the cauldron, said Noguchi. About 2,000 Chinese exchange students swarmed Nagano to show their support.
Minor scuffling and protests broke out during the relay, but the event went ahead without any major interruptions. Five men four Japanese and a pro-Tibetan resident of Taiwan were arrested. Three men were apprehended after trying to charge the torch, the fourth threw eggs and the fifth hurled tomatoes at the flame. All were quickly pounced on by police, police official Akiko Fuseya said.
National broadcaster NHK reported a smoke-emitting tube was thrown at the relay, but that didnt affect it. Marchers yelling Free Tibet crowded the streets near the route. And four people were slightly injured in different scuffles, fire officials said.
The starting point a last-minute substitution after a Buddhist temple pulled out was closed to the public, as were all rest stops along the way. The relay, making its 16th international stop, has been disrupted by protests or conducted under extremely heavy security at many sites since it left Greece.