Amazon on Thursday launched its first "just walk out shopping" outlet outside the United States, as the online retail giant steps up its competition with traditional supermarkets and other retailers.

Customers at Amazon Fresh in Ealing Broadway shopping centre in west London queued outside the black and green storefront under social distancing measures to be first to use the convenience store which has no checkouts.

Londoners waited to try out Amazon's first till-free store outside the US
Londoners waited to try out Amazon's first till-free store outside the US AFP / Niklas HALLE'N

The outlet, according to Amazon, is the "first convenience grocery store to offer just walk out shopping in the UK" and its "first physical shop and grocery store outside of the US".

To use the new outlet, customers have to download an app and then scan a QR code before an electronic gate swings open and allows them to browse a range of Amazon-brand products.

A customer scans her phone containing a special code as she enters the store that lets it know who she is in order to charge her for the goods she takes
A customer scans her phone containing a special code as she enters the store that lets it know who she is in order to charge her for the goods she takes AFP / Niklas HALLE'N

On its opening day, a team of assistants, dressed in vibrant green jackets -- the same colour as the grocery shop's colourful branding -- were on hand to explain how the system worked.

Once they have bagged their items, customers don't have to show a card or let anyone know, they simply walk out.

"It was really strange, it felt like I was a criminal, because I was just taking things and putting them straight in my bag," 71-year-old Ealing resident Philippa Dolphin told AFP.

Cameras keep an eye on what customers pick up from the shelves
Cameras keep an eye on what customers pick up from the shelves AFP / Niklas HALLE'N
As the bag says, customers can just walk out, potentially saving them considerable time they would normally wait to check out
As the bag says, customers can just walk out, potentially saving them considerable time they would normally wait to check out AFP / Niklas HALLE'N

"But apparently there are cameras watching me. And then you just walk out! It didn't seem right but I was assured it was okay!" she added.

Amazon has said the store, which is similar to 20 Amazon Go outlets in the United States, uses "deep learning" algorithms -- technology which allows machines to learn by themselves -- with cameras and sensors to tell what customers have picked up.

"It automatically knows what you've got in your basket and when you leave the shop it charges you and bills you automatically into the account you have set up," said Erica Ely, a 57-year-old local resident, holding her purchases on the street outside the shop.

Amazon's move into 'bricks and mortar' retail in UK could mean even more competition for its rivals
Amazon's move into 'bricks and mortar' retail in UK could mean even more competition for its rivals AFP / Niklas HALLE'N

Benjamin Rogers, 31, a sales manager who lives in the area, stopped in to buy ingredients for a cake and said the speed of shopping at the Amazon store made it appealing.

"I think the major advantage is the fact that sometimes when you go to the supermarket you can do your shopping and then it can be a five-, 10-, 15-minute wait to pay for your goods at the end" he said.

"This is just a simple way to cut through and walk out and finish your job."

Matt Birch, a former Sainsbury's executive who now leads Amazon Fresh Stores UK, said the brand which is also used for online groceries in the UK has looked to make the experience "as convenient as possible".

"We recognise that UK customers want to shop in a convenient way so we really think they will appreciate being able to walk in and walk out with the shopping they need," he added.

Amazon, which was already growing in Britain before the pandemic and competing with a struggling retail sector, has seen its position strengthen since the outbreak and months of closure for shops deemed non-essential.

Shopper Mark Lloyd said it was "interesting" that Amazon was moving from online into "bricks and mortar retail business".

"It is kind of reversing the trend for e-commerce and digital shelves, so it is quite unusual in that respect," the 58-year-old creative director said.

Despite the ease of her shopping experience, Dolphin said she was somewhat troubled what about the arrival of the Amazon shop would mean in the long term.

"I am a bit worried that it is going to put other businesses that I use out of business. So yes, I am a little bit concerned because they are such a giant," she said.