LATE last year thousands of pro-democracy demonstrators poured onto the streets of Hong Kong calling for the right to elect the city’s leader in 2017, free of interference by the central government in Beijing. In recent weeks protests have flared again; far smaller this time, but more violent and similarly fuelled by resentment of the mainland’s encroachment. At issue has been the hordes of mainland Chinese who visit Hong Kong to buy goods for black-market resale at home, a racket described locally as “parallel trading”. These new and nastier outbursts are about far more than shopping; they suggest that antagonism towards the mainland is deepening and spreading beyond the territory’s urban core. This is causing anxiety among officials on both sides of the border.

In 2002, five years after the end of British colonial rule, the Hong Kong government abolished a quota on Chinese tourists. Since 2009 residents of Shenzhen, a city adjoining Hong Kong, have been able to cross the border as often as they like. The loosening of restrictions has been credited by Hong Kong officials with reviving the city’s flagging economy. But many Hong Kongers feel they are being swamped. Chinese visitors have increased tenfold since 2000; last year there were 47m, an increase of 16.5% over 2013, in a city of 7m people. Some reckon there will be 100m a year by 2020. The visitors, however, are spending less on average per person than they were in 2009. China’s anti-corruption campaign has quashed demand for luxury items. In December sales of such goods fell by 16.3% year-on-year.

To the annoyance of Hong Kongers, a new type of shopper has appeared: those who come to buy household staples, taking advantage of Hong Kong’s 0% sales tax (mainland China’s is 17%). Some join organised teams, each person taking back a suitcase-full of goods for collection by middlemen on the other side. They buy not just for price, but for quality. Many Chinese do not trust home-made goods. In 2008 Hong Kong suffered shortages of infant formula after mainland supplies were contaminated. The city responded by imposing strict limits on formula exports.

The demand is changing the territory’s shopping environment. In San Hong Street in Sheung Shui, an area near the border, shop after shop is piled high with nappies, milk powder, toothpaste and washing-up liquid. Store-owners are happy with the frenzied custom, but many locals are not. Rents have risen and many older outlets have closed. Shops catering to mainland visitors “lock out Sheung Shui culture”, says Leung Kim Shing of the North District Parallel Imports Concern Group.

Most Hong Kongers moved from the mainland in the past century, but the gap between the two sides is growing. A poll last year found that ever fewer Hong Kongers identify themselves as “Chinese”. Many complain about what they see as the boorish behaviour of their mainland compatriots and brand them as “locusts” for stripping shelves. Some ensuing confrontations have been nasty. Scenes caught on camera in February showed a crowd yelling and heckling a mainland woman and her crying daughter. Mainlanders have been verbally abused and jostled by masked protesters. “People are angry and bitter,” says Emily Lau of the Democratic Party and a member of Hong Kong’s Legislative Council. She notes the spread of such sentiment into areas near the border where identity with the mainland used to be stronger than in the more densely populated city, the usual site of protests relating to mainland China.

Hong Kong’s government is in a bind. The shoppers may be irritating, but few are doing anything illegal in Hong Kong. Mainland regulations allow visitors to bring back goods worth up to 5,000 yuan ($800). Many shoppers, even black-market traders, keep to this. Enforcement of the limit is, in any case, weak. Hong Kong’s government does not want to pander to anti-mainland sentiment by siding with the protesters. But it also does not want to fuel the pro-democracy movement by ignoring public grievances. Income inequality in Hong Kong is gaping, the population is ageing rapidly and property prices are steep. Many blame mainlanders for exacerbating these woes. Around 40,000 Shenzhen residents work in Hong Kong and 20,000 Shenzhen children attend school there. All of this contributes to a growing feeling, particularly among young people, that Hong Kong’s government has sold out to the one in Beijing.

The central government is sensitive to Hong Kong’s predicament. This month a senior mainland official responsible for Hong Kong affairs, Zhou Bo, was quoted as saying that Hong Kong’s tourist capacity had “by and large reached saturation”. But altering the visa system would be unpopular with mainlanders, especially residents of Shenzhen. Chinese officials have given no hint that they are considering any changes on their side.

Even if a way is found to stem the onrush of shoppers, Hong Kong faces a difficult year. Discussions in the legislature about arrangements for the election in 2017 are due to be finalised by the summer, and could be a catalyst for more unrest (China has shown no sign of compromise on its restrictive plans for the polls). Other flashpoints include a review due in June of how Chinese history is taught in schools; some students fret that this will involve renewed efforts to introduce “patriotic” education. On June 4th Hong Kongers will hold their annual rally to mark the crushing of the Tiananmen Square protests in 1989. July 1st, the anniversary of Hong Kong’s handover to China, is often an occasion for big demonstrations as well. The government will have little respite.