FLINTSHIRE and Wrexham will go into lockdown on Thursday at 6pm.
Local lockdowns will also be imposed on Conwy and Denbighshire.
READ These are the lockdown restrictions for North Wales counties
Health Minister Vaughan Gething has just made the announcement to the Senedd.
He said the decision followed a meeting he and FIrst Minister Mark Drakeford had with local authorities and police.
Vaughan Gething today
The announcement on Tuesday evening will affect around 504,000 people and will bring the number of people in Wales under lockdown to more than 2.3 million.
And it means 16 areas of the country will face restrictions, with the four local authorities joining Caerphilly county borough, Rhondda Cynon Taf, Bridgend, Merthyr Tydfil, Newport, Blaenau Gwent, Cardiff, Swansea, the town of Llanelli, Neath Port Talbot, the Vale of Glamorgan, and Torfaen, all in South Wales.
Mr Gething said: “Unfortunately, we have seen a rise in coronavirus cases in four north Wales local authority areas – in Denbighshire, Flintshire, Wrexham and Conwy.
“These are largely linked to people socialising indoors and are the pattern of transmission similar to what we have seen in South Wales.
“We have worked closely with local authority leaders and the police in North Wales and we all agree about the need to take swift action to control the spread of the virus.”
Under the rules, nobody is able to enter or leave the counties without a "reasonable excuse".
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Exceptions include travelling to school or to work if you are unable to work from home.
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