Apple gave consumers their first hands-on look at its smartwatch Friday pushing into wearable tech just as rival Samsung rolled out its new flagship smartphones.

With the world's two biggest gadget makers vying for consumer attention, Apple scored points by apparently selling out of the Apple Watch as quickly as it opened pre-orders.

Customers ordering the watch, due to go on sale April 24, saw messages saying deliveries now were being pushed back into June or later.

"I really debated if I should buy the thing," said Eric Angelosanto, one of the customers looking to try the smartwatch at a New York Apple store, who indicated that he had already placed an order online.

"It's tremendously overpriced, but a treat."

The Apple Watch starts at $349, with a limited-edition gold version priced at $12,000.

Angela Ahrendts, Apple's senior vice president of retail and online stores, said she expects "that strong customer demand will exceed our supply at launch."

Some analysts were not so sure about prospects for the new wearable device.

"The watch's success is anything but guaranteed," said Roger Kay, analyst at Endpoint Technologies Associates.

"Most people I've talked with are not ready to buy one. It seems expensive, redundant and perhaps invasive."

In Paris, at the company's flagship store by the Place de l'Opera journalists outnumbered customers, with Apple encouraging customers to place orders online and with stores offering only demonstrations.

Would-be early buyers queued for a "trial fitting" at the Apple store in Tokyo's chic Omotesando area.

"I'm very keen to buy it," said Kazuki Miura, a 43-year-old technology writer, as he slipped the device onto his wrist.

Apple's device, which connects to the iPhone to facilitate messaging, calls and apps geared toward health and fitness, is a latecomer to the smartwatch market, and follows launches from Samsung, Huawei, Motorola, LG and others including the crowd-funded Pebble watch.

And not only tech companies: last month luxury Swiss watchmaker TAG Heuer announced it was joining forces with Google and Intel to develop a rival to the Apple Watch.

But because of Apple's devoted customer base, analysts expect the new watch to quickly take the lead and sell millions.

- Samsung's Galaxy S6 debuts -

Meanwhile, Samsung's Galaxy S6 and its curved-edge variant, the Galaxy S6 Edge, went on sale in South Korea, home of the electronics giant, as well as Europe, the United States and markets in the Asia-Pacific such as Australia, Singapore and India.

Samsung, laboring under successive quarters of plunging profits and booming sales of Apple's iPhone 6, is hoping the new phone will reverse its fortunes.

"Given the response from the market and clients... we expect the S6 to set a sales record for all Galaxy models," Lee Sang-Chul, the vice head of Samsung's mobile unit, told reporters.

Joo Seung-Bin was one of the first in line to buy an S6 in Seoul on Friday morning.

"It's a great design, and it's just got a great feel," the 23-year-old said.

"It's not cheap, but then I'm not one of those people who upgrades their phone every year. There's been a lot of buzz about this model, so I thought I'd check it out," Joo said.

The S6 retails at around 858,000 won ($800) in South Korea, while the S6 Edge comes in at 979,000 won, broadly in line with their Apple counterparts.

Both models are powered by Google's Android operating platform and, in a break from their-plastic-backed predecessors, feature metal and glass bodies.

"Demand for the new Galaxy model is considerable," said a spokeswoman in Germany for Media Saturn, the largest electronics retailer in Europe, although she said stocks had not been sold out.

Samsung has been struggling to stay atop the global smartphone market amid a surge last year from Apple after the release of new large-screen iPhones.

But, despite fierce competition on various market fronts, there are signs that Samsung is beginning to fight back. Earlier this week it released a better-than-expected profit estimate for the first quarter.

Samsung suffered a dramatic slide in profits last year, hit by slowing demand in an increasingly saturated and competitive smartphone market that it had largely dominated since 2011.

The company is seeking to fend off a double challenge from Apple in the high-end market and rising Chinese firms such as Lenovo and Xiaomi in the fast-growing mid and low-end markets.

Samsung rarely discloses handset sales figures but analysts say the Galaxy S4, released in 2013, set the firm's sales record of 70 million units globally.

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