New coronavirus restrictions have been announced for Leeds, parts of Wales and more towns in the north-west, bringing the numbers affected by stricter measures to 21.3 million, as London was placed on the government’s “watchlist”. Cardiff and Swansea will be subject to local lockdowns, the Welsh government has announced. From 6pm on Sunday, residents in the Welsh cities will not be able to travel in or out without reasonable excuse, or able to meet indoors with anyone they do not live with. Some parts of Llanelli in south Wales will also be under a local lockdown from Saturday evening. The new restrictions will affect about 800,000 people. Restrictions on household mixing were announced for Blackpool, Wigan, Stockport and Leeds. Matt Hancock, the health secretary, said the latest data “shows a sharp increase in incidence rates per 100,000 population” in the four areas, which are significantly above the national average. Regulations, which take effect from Saturday 26 September, will mean people will not be allowed to gather in a private dwelling or garden with any other household unless in a support bubble. Restrictions are already in force across large swaths of north-west England, West Yorkshire, the north-east and the Midlands, as well as parts of west Scotland. It means an estimated 21.3 million people across the UK will be living under additional coronavirus measures by Sunday evening, on top of those announced by Boris Johnson. No additional measures are being taken at this stage in London, but the city’s mayor warned on Friday that household visits must soon be banned for its 9 million residents. Tom Riordan, the chief executive of Leeds city council, said: “What we are trying to do is give a simple message – you shouldn’t really mix with other households.” He said about 780,000 people would come under the new measures, which could be in place throughout winter. Riordan said: “I think we know from the experience of Leicester, Greater Manchester and West Yorkshire that when these restrictions are brought in they do not tend to be lifted after a week or two.” The city’s virus rate was 98.5 per 100,000 people, with a positive testing rate of 8.4%, Leeds council’s director of public health, Victoria Eaton, said. The spread was “very dynamic” with “high rates in some of our student areas”, but cases were rising in all age groups, she added. London Councils, a cross-party organisation that represents all 32 boroughs and the City of London, said the English capital was being placed on the national Covid-19 watchlist. The list is divided between areas where intervention is required via local lockdown restrictions and areas of concern that are closely monitored. London Councils said it was a “stark reminder” to Londoners to pull together. A statement said: “There are no additional measures at this stage but it is welcome that the city’s testing capacity is boosted so that Londoners have timely access to Covid-19 tests and the government must ensure that this is sustained from now on.” Data shows the estimated number of cases of coronavirus across England has jumped 60% in one week. There were about 9,600 new coronavirus infections a day in England, up on 6,000 the week before, according to the Office for National Statistics (ONS) infection survey. The survey, which tests thousands of people in homes in England, whether they have symptoms or not, found an estimated 103,600 people had Covid-19 between 13 and 19 September, equating to about one in 500 people. The ONS said: “The estimate shows the number of infections has increased. In recent weeks, there has been clear evidence of an increase in the number of people testing positive for Covid-19 in all age groups, with the current rates highest in the 17-24 age group. “There is evidence of higher infection rates in the north-west, Yorkshire and the Humber, London and north-east.” Sadiq Khan, the mayor of London, tweeted: “The government need to urgently increase testing availability in the capital – and Londoners must act with caution and follow public health guidelines.” On Sunday he said London was just two or three days behind hotspots such as the north-east and Greater Manchester. Kevin Fenton, the director of Public Health England in London, said this week all signs indicated the virus was making a resurgence in the city. He said: “We are seeing a rising tide of coronavirus cases in London across a broad range of ages. This is no longer limited to young people in their 20s. Infections across the city have more than doubled since August, with the highest rates in Redbridge, Hounslow and Barking and Dagenham . The number of people in hospital with the virus is said to have tripled in a fortnight, though admissions are much lower than in March.