Living and working just a few hundred metres from Hong Kong, residents of neighbouring Chinese boomtown Shenzhen are infuriated by new restrictions on travel to the former British colony.
Nearly two decades after the territory was reunited with the mainland under a "one country, two systems" system, the model is straining at both ends, with Hong Kongers taking to the streets to demand greater democracy, and mainlanders visiting in their millions.
The influx has raised tensions in Hong Kong, prompting protests by residents hostile to Beijing's mounting influence and the tide of mainland consumers snapping up the territory's supplies of baby milk powder, iPhones and hospital beds.
Earlier this month, Beijing responded by halting permits that had let Shenzhen residents make unlimited trips to Hong Kong, restricting them instead to one visit per week.
Authorities said the move was made at Hong Kong's request, and Shenzhen residents are resentful.
"No matter if we are mainlanders or Hong Kongers, we are all Chinese," said a 40-year-old Shenzhen resident surnamed Wu. "If we have documents to show that, we should be able to travel freely."
Wu is one of the many "parallel traders" who make a living importing goods into China from low-tax Hong Kong, where items are often cheaper and safer than their mainland equivalents.
Another shouted: "How can Hong Kong have such a policy? What kind of a country is this?"
Their business -- and sometimes behaviour -- has enraged Hong Kongers, who accuse the mainlanders of pushing up prices and stripping shop shelves, with some residents even holding violent protests in shopping malls.
Wu and other traders gathered in a concrete underpass near the border post of Luohu -- known as Lo Wu in Hong Kong -- asked for their names to be withheld due to the questionable legality of the trade.
But they insisted it would continue.
"It's the Hong Kongers who do the parallel trading, not us Shenzheners," said a female trader surnamed Huang.
- 'Symbolic appeasement' -
Milk powder became a cherished Chinese import after a 2008 poisoning scandal killed six children and affected more than 300,000 others, destroying trust in local brands.
A steady stream of border-crossers -- several identifying themselves as Hong Kong residents -- whipped out tins of milk powder and offered them to the eager recipients.
Lin Xiaofeng, a 22-year-old Hong Kong student, said she made "a bit of money" by bringing goods over the border, but added: "I think the weekly visit policy is good. It will help reduce the number of mainlanders in Hong Kong."
But policy differences were no obstacle to free trade, and her two cartons were rapidly exchanged for several crisp red yuan notes.
Mainlander visits to Hong Kong -- population 7.3 million -- have more than doubled in the past five years, according to Hong Kong's census department, from 22.7 million in 2010 to 47.2 million last year.
Steve Tsang, director of the China Policy Institute at the University of Nottingham, described the new restrictions as "a partial and delayed response" to Occupy Central, the pro-democracy protest movement that shook Hong Kong late last year.
More than two months of demonstrations followed Beijing's announcement that candidates for election as Hong Kong's leader in 2017 would first have to be vetted by a pro-Beijing committee.
"The symbolic appeasement of the general public will be well received and in that sense help. But the real effect is likely to be limited," said Tsang.
He added that the restrictions appeared to have been timed to coincide with last week's release by the Hong Kong government of its roadmap for the 2017 vote, which abided by Beijing's limits.
"In any event, there are a wide range of issues that cause a negative feeling towards mainlanders in Hong Kong, and the activities of the parallel traders is only one of them," he said.
Shenzhen parents whose children were born in Hong Kong and go to school in the city can still apply for unrestricted three-month visit permits, but one such mother, surnamed Fu, nonetheless described the new policy as "unreasonable".
"When we moved to Shenzhen we were promised unlimited access to Hong Kong."