China is to stop issuing multiple entry Hong Kong visas to residents of Shenzhen, state media reports.
The move is an attempt by Beijing to ease growing anger in Hong Kong over shopping trips by mainlanders who take advantage of lower taxes.
Shenzhen residents will now only be able to enter Hong Kong once per week, and stay for no longer than a week.
Hong Kong officials say 47 million visits were made in 2014 by mainland Chinese people.
Juliana Liu, BBC News, Hong Kong
Hong Kong activists who have been campaigning against parallel traders are celebrating what they call a small victory. The new policy is a clear sign that, despite a lack of capitulation to last year's Occupy Central pro-democracy protests, this time - when the row is over livelihood rather than political issues - the Chinese government will try to appease Hong Kong residents. Ronald Leung, a volunteer with the North District Parallel Imports Concern Group, told the BBC the policy change was an effort by central authorities to boost the popularity of pro-Beijing Chief Executive CY Leung. But the activists believe any drop in parallel trading will be temporary. There continues to be enormous demand by mainland Chinese for food and household goods sold in Hong Kong. They say the Shenzhen residents who had been ferrying those products will soon be replaced by Hong Kong residents who are not subject to travel restrictions.
About a tenth of those visits were by people who entered Hong Kong more than once a week, a large proportion of them Shenzhen residents holding multiple entry visas.
Many of the visitors buy up household goods in bulk to resell across the border - as Hong Kong does not charge sales tax - despite this being illegal.
There have been angry protests in recent months over this so-called parallel trading, occasionally resulting in scuffles in shopping malls close to the border.
China's Xinhua news agency, citing the ministry of security, said on Monday that the new rules applied immediately.
It said the decision had been made because of concerns that Hong Kong was struggling to cope with the huge numbers of tourists.
Hong Kong's Chief Executive CY Leung welcomed the move, saying he had raised the issue with Beijing in June.
Mainlanders have to get permission from their government to enter Hong Kong.
Mr Leung warned that existing visas would remain valid, meaning it could take some time for the effect of the change to be seen.
He also cautioned that the "unruly protests" seen in towns close to the border had actually hampered the discussions and "hurt the feelings between the people of Hong Kong and the mainland", the South China Morning Post reports.
Parallel trading has been a key factor in the growing anti-mainland sentiment in Hong Kong.
There is huge demand in China for household items from Hong Kong, in particular milk powder, as they are seen as being both cheaper and better quality.
Hong Kongers say this trade pushes up costs and causes huge delays at border crossings, while also complaining about poor behaviour from mainlanders.
The authorities on both sides of the border routinely arrest people caught smuggling and crack down on commercial operators, but locals have long demanded more decisive action.