The areas of Bridgend, Merthyr Tydfil, Newport and Blaenau Gwent will be placed under a local lockdown following an increase of coronavirus cases, the Welsh Government has announced.
Health minister Vaughan Gething said there had been a 'worrying and rapid rise' in cases of Covid-19 in the four areas in south Wales.
The measures - that will impact more than 400,000 people - come into force at 6pm on Tuesday. People must not enter or leave the areas without a reasonable excuse.
And people are only able to meet outdoors and are unable to meet members of their extended household indoors.
Health minister Vaughan Gething (pictured) said there had been a 'worrying and rapid rise' in cases of Covid-19 in the four areas
The town of Bridgend (pictured) is one of the areas that will go into a local lockdown
Cars at a drive-thru coronavirus testing station at Ebbw Vale in Wales. New coronavirus lockdown restrictions will come into force
All licensed premises will have to close at 11pm.
Mr Gething said many of the coronavirus cases had been linked to people socialising indoors without physical distancing.
'We are seeing evidence of coronavirus spreading,' Mr Gething told a press conference in Cardiff.
'We need to take action to control and, ultimately, reduce its spread and protect people's health.
'It's always a difficult decision to introduce restrictions but coronavirus has not gone away - it is still circulating in communities across Wales and, as we are seeing in parts of South Wales, small clusters can quickly cause real issues in local communities.'
The Welsh Government will call an urgent meeting of all local authority, health board and police forces from Bridgend to the English border on Tuesday.
People on the high street in Merthyr Tydfil, Wales, which will be one of the next areas to have a local lockdown
This will discuss 'the wider situation in south Wales and whether further measures are needed across the region', the government said.
Last week, Caerphilly county borough and Rhondda Cynon Taf were also placed under local lockdown.
It comes just hours after the Sir Patrick Vallance said the UK could see 200 or more deaths per day by mid-November if the current rate of infection is not halted,
The Government's chief scientific adviser said the 'vast majority of the population remain susceptible' to catching coronavirus and the current situation required swift action to bring the case numbers down.
He added that if current infection rates continue, the UK could see around 50,000 cases a day by the middle of October.
It comes as ministers make final decisions on what national measures are needed to tackle rising cases, with Health Secretary Matt Hancock strongly hinting that separate households could be prevented from mixing.
In the first televised address alongside England's chief medical officer Professor Chris Whitty that was not attended by politicians, Sir Patrick said there was 'no doubt' the UK was seeing increasing cases of Covid-19 among all age groups.
He said it was 'not a prediction', but the current doubling of cases every seven days could lead to a dramatic rise in hospitalisations and deaths.
In mid-September, around 3,000 new cases were recorded every day in the UK, he said.
Sir Patrick Vallance today warned the UK could face 50,000 new coronavirus cases by mid-October if the spread of the disease is not curtailed. He is pictured alongside Professor Chris Whitty in Downing Street this morning
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Official Downing Street slides showed that if the current rate of infection continues there could be 50,000 coronavirus cases every day by the middle of October and that could lead to 200 plus deaths a day by the middle of November
'If - and that's quite a big if - but if that continues unabated and this grows, doubling every seven days, then what you see, of course, let's say there were 5,000 today, it would be 10,000 next week, 20,000 the