Long queues formed outside well before it opened at 8.30am, and staff members were handing out free water to people waiting in line.

The queues, surrounded by steel fences, moved slowly and more than 20 police officers and community volunteers were deployed at an intersection about 300 metres (984 feet) away from the store to help maintain the flow of traffic.

One policeman on duty said officers were expected to stand guard at the site for two to three days.

A police officer said at 2.40pm that it would take at least two hours to get into the store.

Hongkonger Carol Ng and her husband, who arrived at around 10.30am and queued for two hours before they got in, were among the shoppers.

“We saw the promotion online, so we came to take a look out of curiosity,” she said. “We bought a lot of fruit, bread and snacks for the children today because Lunar New Year is coming soon.”

Hongkongers hunt for roast chicken, other bargains at US warehouse store in Shenzhen

Ng, 66 and retired, added she spent between HK$600 (US$77) and HK$700 on products, which she estimated would have cost about HK$2,000 in Hong Kong.

She added she often signed up for tour groups to shop at Sam’s Club, another warehouse-style store in Shenzhen, owned by American supermarket giant Walmart.

Ng said the experience at Costco was not much different from Sam’s Club and that she planned to return to Hong Kong as soon as the shopping trip was completed.

Products cleared from the shelves ranged from food and daily supplies to luxury goods, including handbags, watches and jewellery.

Philip Lau, 35, who runs an online store, said he made the trip to find deals on daily necessities, despite the prospect of the long wait.

“Hongkongers like to explore new things,” he said. “A friend told me this Costco was opening so I came here out of curiosity.

“I’ll buy some basic needs like food or washing powder. I think usually they will be at least 30 per cent cheaper on the mainland than in Hong Kong.”

Retiree Zhao Yingchun from Shenzhen, who went shopping at the store with friends, complained about the huge crowds and how quickly the limited number of discounted products sold out.

“For example, strawberries, you will get 30 yuan cheaper per 500 grams, but it was sold out quickly before noon, and only 100 bottles of Mao-tai liquor advertised by Costco were provided, which is far from enough for customers,” the 62-year-old said. “I just bought some fresh shrimp. Products here are not cheaper than Sam’s Club.”

Hongkongers flock to Shenzhen where their dollar takes them further

Shenzhen resident Wu Yongtao, 31, was also among the bargain hunters who descended on the new store.

“We bought some toys and daily necessities for the children, such as fruit and meat, and it cost me about 500 yuan,” Wu, who lives nearby, said. “To be honest, I was a little disappointed because the queue was really long and my shopping experience was not worth it. We waited in line for almost three hours.”

Shop till you drop: mainland bulk retailer trips a hit with young Hongkongers

Wu agreed Costco was similar to Sam’s Club, which had similar products and prices.

The Shenzhen store is Costco’s first in south China and the sixth on the mainland. The four-storey branch, with a floor area of 44,500 square metres (478,994 sq ft), features about 4,000 brand-name products sourced from Chinese and international manufacturers.

Massive members-only bulk retailers across the border have become increasingly popular among Hongkongers because of the cheap deals on offer.

The Hong Kong dollar’s strength against the yuan has also helped make shopping on the mainland more attractive.

Sam’s Club has already caused Hongkongers to head north to hunt for bargains, as well as for items only available on the mainland.

The buzz has sparked a trend among city travel agents to include shopping sessions at the store in its itineraries to cater to the appetite for splashing out over the border.