Technology fans in Japan were among the first to get the top-of-the-range iPhone 5S, as well as the new "budget" version, the 5C.
Apple stores in the UK opened early, with estimates of 1500 people outside one London store.
Some British Apple fans pitched up several days before the launch; some in Tokyo queued for 10 days.
In California an overnight campout turned chaotic when two men were arrested for fighting outside an Apple Store and a man's plan to hire homeless people to wait in line for the coveted devices backfired, authorities said.
Dozens of people recruited at a downtown Los Angeles homeless shelter to buy iPhones in bulk at a Pasadena store were left unpaid, and they mobbed the man who had hired them, Pasadena police Lt Jason Clawson said.
One of the homeless men was placed on a 72-hour mental health hold after running into the street in an enraged state, Clawson said. Television news footage showed police breaking up several scuffles.
Dominoe Moody, 43, told the Los Angeles Times he was driven 16km to Pasadena from Los Angeles with several vanloads of people to wait in line overnight on Friday.
Moody was promised US$40 but said he wasn't paid because after handing the man an iPhone, police escorted the man away when people became angry.
The would-be entrepreneur was clutching a bag stuffed with iPhones when he was escorted into a police cruiser.
Most of the people recruited weren't paid, Moody said, estimating that the man brought 70 to 80 people to the store.
