Apple's new iPhone went on sale today, with fans snapping up the final gadget unveiled during Steve Jobs' lifetime, many buying the phone as a tribute to the former Apple boss.

Hundreds queued around city blocks in Sydney and Tokyo to get their hands on the iPhone 4S, ahead of store sales in Germany, France, Britain and North America.

"I am a fan, a big fan. I want something to remember Steve Jobs by," said Haruko Shiraishi, waiting patiently with her Yorkshire terrier Miu Miu at the end of an eight block queue in Tokyo's smart Ginza shopping district.

The new model looks similar to the previous iPhone 4 but has an upgraded camera, faster processor and highly regarded voice-activated software, which allows users to ask questions.

Australian Tom Mosca, the first to buy the phone in Sydney, said he would ask his new white iPhone: "Where's Steve?" Many Apple fans believe the phone was called iPhone 4S to mean "for Steve".

Apple CEO Tim Cook and his executive team hope the first device sold without their visionary leader at the helm will protect them against a growing challenge from the likes of Samsung Electronics.

The South Korean firm, Apple's arch-rival with smartphones powered by Google's Android software, expects to overtake it as the world's biggest smartphone seller in terms of units sold in the third quarter.

The iPhone 4S - introduced just a day before Mr Jobs died - was dubbed a disappointment because it fell short of being a revolution in design, but glowing reviews centred around its "Siri" voice-activated software have helped it set a record pace in initial, online sales orders.

In Tokyo, 24-year-old Ryosuke Ishinabe said: "I just wanted the newest iPhone. I want to try out iCloud."

Despite the enthusiasm at Apple stores, the launch was marred somewhat by widespread complaints this week on the Internet about problems downloading iOS 5 - the latest version of Apple's mobile software.

There were also problems with iCloud, Apple's online communications, media storage and backup service formally launched Wednesday, with users reporting glitches such as losing their email access.

Those concerns pale compared to the problems for rival Research in Motion, which has been grappling with an international outage of its Blackberry email and messaging services for several days.

The vast majority of the iPhone 4S buyers at the Sydney store appeared to be existing Apple customers, many having bought the original iPhone and its subsequent upgrades. Only one out of 10 people surveyed by Reuters was a new Apple customer.

"I have been waiting for the iPhone 5 for a long time. But since Jobs died, I wanted to make sure I had a new iPhone with some advantages over the old," said iPhone devotee Mark Du, concerned over future Apple gadgets without Jobs in charge.

Apple fans in Sydney and Tokyo made sure Jobs was part of the iPhone 4S launch, with flower, candle and photo shrines to the late Apple boss erected outside the stores.

Underscoring the enthusiasm for the new phone, Japanese mobile carrier Softbank Corp had to temporarily stop contract applications after its computer system was overwhelmed with more requests than it had expected.

Apple said it did not release sales figures on launch day, so gauging initial sales is difficult. Apple said it had taken more than 1 million online orders in the first 24 hours after its release, exceeding the 600,000 for the iPhone 4, though that model was sold in fewer countries initially.

Some analysts expect fourth-quarter iPhone shipments to reach 30 million or more, almost twice as much as a year ago.

Apple's fifth-generation iPhone uses chips from Qualcomm, Toshiba and a host of smaller semiconductor companies, according to repair firm iFixit, which cracked the device open yesterday.

Apple's iOS 5 software became available this week and is intended to upgrade older phones and enable new features such as better Twitter integration.

But glitches with the new iCloud service and mobile software sparked a chorus of user complaints.

"This would be a great time for like, Samsung or something, to take out a sponsored ad," user Ryan James Kirk tweeted.

The iPhone - seen as the gold standard for smartphones - is Apple's highest-margin product and accounts for 40 per cent of its annual revenue.

In a sign of how tough the competition is, two doors along from the Sydney Apple store, Samsung has been selling its new Galaxy SII for only A$2 to its first 10 customers each day, prompting Samsung fans to also camp out on the footpath.

Reuters