A FRUIT-SELLER walks from his stall, across a snowy courtyard, to a shabby little building overshadowed by apartment blocks. A sign advertises “semi-underground rooms”, but the building is the entrance to an air-raid shelter built at the height of Sino-Soviet tensions deep beneath the courtyard, where the merchant lives in a tiny windowless room with his wife (like the couple pictured). If the Beijing authorities have their way, he will not be in the shelter for much longer.

City officials are deluged with complaints about traffic jams, crowded public transport and creaking schools and hospitals. In recent months they have revived long-neglected pledges to control the growth of the city's population. They do not say so openly, but Beijing's leaders are busy erecting new barriers to entry for unskilled workers. In December plans were revealed to close down the shelter dwellings within a year. Officials also made it clear that basement accommodation would go too. The local media say the measures could affect more than 1m people.

The fruit-seller is worried. If they close his air-raid shelter, where his room occupies 12 square metres (130 square feet) and costs 330 yuan ($50) a month, he says, he will have no choice but to return to the village in the southern province of Jiangxi from where he and his family moved five years ago. “They want to get rid of outsiders,” he says bluntly. His landlady says that many of her underground tenants share his view.

Rarely since the 1980s, when China's strict controls on migration from countryside to town began to break down, has the capital appeared so determined to reverse the tide. A key event was an investigation last summer which found that Beijing's population (those living in the city for six months or longer) had topped 19.7m by the end of 2009. This was 2m more than official figures had suggested. In a development plan published seven years ago, the government had aimed not even to reach 18m before 2020. The figures are a bit misleading, because Beijing municipality covers an area half Belgium's size, with far-flung satellite towns and a rural expanse. But even the city proper has grown to more than 10m, from 8.5m a decade ago.

In October a Communist Party resolution called on smaller cities to embrace more migrants and for bigger ones to control their influx. That stiffened Beijing's resolve. So too, said Caijing, a fortnightly magazine, did the dissatisfaction expressed by party leaders with Beijing's traffic congestion. (Never mind that official events and cars are big contributors to the jams.) Chinese leaders have always been especially sensitive about rural migrants in the capital, fearing they might include dangerously disgruntled elements. Many underground housing facilities were temporarily closed down before Beijing's Olympic games in 2008 and again in 2009, before the 60th-anniversary celebrations of communist China's founding.

In late December officials introduced swingeing new measures to ease the traffic. These included limiting the number of licence plates issued this year to just one-third the number in 2010. To qualify for plates, migrants need to have lived in the city for five years, with evidence that they have a job and have paid taxes. It bars most from buying a car. The new rules also ban out-of-town cars in much of the city during peak hours.

During meetings of Beijing's district and city-level legislatures in January, a frenzy of calls by party-picked delegates demanded tighter population controls. An old slogan was dusted off about using housing, employment and identity papers to keep numbers in check. Closing down underground accommodation, officially on health and safety grounds, was touted as one useful technique. Another was a crackdown on partitioning flats for rent. On February 16th the government announced that homebuyers would be subject to similar restrictions as people buying cars. For the first time in years, says Century Weekly, another magazine, officials are talking about making the hukou, a proof of domicile that is hard to obtain when not inherited and that confers all sorts of health and welfare rights, even more difficult to get.

Last year some officials praised Shunyi, a semirural suburb popular among expatriates, for controlling population growth. It had hindered the founding of the small, service businesses that attract migrant labour (though a commentary on the website of one national newspaper likened the “Shunyi model” to South African apartheid). In January Fangshan, another suburb, declared that it would use similar techniques to eliminate what it calls the “five little enterprises and six small places” by 2015. These include labour-intensive industries and small restaurants and guesthouses. A Beijing deputy mayor was quoted as saying in January that the whole city would raise the threshold for permits for such businesses, which employ hundreds of thousands of migrants.

Beijing's exclusionary bent has its critics. Hundreds of angry landlords of underground housing have petitioned the government to change its mind. Even the state-controlled press has aired dissent. One scholar has been quoted as saying that the capital's fixation on a numerical limit has no scientific basis and that market forces should determine its population. Others say the ban on underground housing is unenforceable (some members of the “rat tribe”, as the Chinese press sometimes calls the subterranean dwellers, agree). Still more complain that the government's heavy hand is pushing up rents for other kinds of budget accommodation.

A year ago a daring joint-editorial published by several newspapers in defiance of Communist Party wishes called for the hukou system to be scrapped. It fell on deaf ears. In October Chen Gui, a senior cadre in the China Real Estate Association, wrote that the number of “low-income, low-quality and ill-educated outsiders” should not be allowed to increase in megacities like Beijing. That, it seems, is more like the official line.