A two-week "firebreak" lockdown will be introduced across Wales from 6pm on Friday, First Minister Mark Drakeford has said.
Mr Drakeford told a Welsh Government press conference in Cardiff that the measure was necessary to reduce the spread of coronavirus and prevent the NHS from becoming overwhelmed.
The "sharp and deep" lockdown will begin at 6pm on October 23 and last until November 9, with everyone in Wales "required to stay at home".
"The only exceptions will be critical workers and jobs where working from home is not possible," Mr Drakeford said.
Mr Drakeford said the lockdown would be a "short, sharp, shock to turn back the clock, slow down the virus and give us more time".
There were 4,127 new confirmed cases of coronavirus recorded by Public Health Wales between October 9 and 15, though the real level of infections is believed to be much higher.
The R value – the number of people each coronavirus case infects – across Wales is currently between 1.1 and 1.4, while the seven-day rolling incidence rate for Wales is more than 130 cases per 100,000 people.
"There are no easy choices in front of us, as the virus spreads rapidly in every part of Wales," Mr Drakeford said.
"We know that if we do not act now, it will continue to accelerate and there is a very real risk that our NHS would be overwhelmed.
"The number of people being taken to hospital with coronavirus symptoms is growing every day, our critical care units are already full.
"We are asking our healthcare and social care staff, who have already done so much, to work even harder.
"Unless we act, the NHS will not be able to look after the increasing number of people who are falling seriously ill."
❓ Coronavirus circuit break: frequently asked questions
❓ Cyfnod atal y coronafeirws: cwestiynau cyffredinhttps://t.co/y3ctuNgx0D
— Mark Drakeford MS/AS 🏴 (@MarkDrakeford) October 19, 2020
Mr Drakeford said that "even more extreme measures", such as an open-ended lockdown, would have to be implemented if action was not taken now.
Under the "firebreak" lockdown, all non-essential retail, leisure, hospitality and tourism businesses will close "just as they had to during the March lockdown".
Community centres, libraries and recycling centres will also close, while places of worship will also be shut, other than for funerals or wedding ceremonies.
Childcare facilities will stay open, with primary and specialist schools reopening after the half-term break.
Secondary schools will also reopen after half-term for children in years seven and eight, as well as the most vulnerable students.
Pupils will be able to go in to take exams but others will learn from home for an additional week, Mr Drakeford said.
Universities will provide a blend of in-person and online learning but students will be required to stay at their accommodation.
People will not be able to meet indoors or outdoors with anyone they do not live with, with exceptions for those living alone.
They must stay at home, except for limited purposes such as exercise, and must work from home wherever possible.
Gatherings are banned, including Halloween and fireworks or Bonfire Night celebrations.
"This firebreak is the shortest we can make it but that means that it will have to be sharp and deep in order to have the impact we need it to have on the virus," Mr Drakeford said.
Businesses affected by the firebreak will be supported with a fund of almost £300m, which will open next week.
Every business covered by the small business rates relief will receive a £1,000 payment, while small and medium-sized retail, leisure and hospitality businesses that have to close will receive a one-off £5,000 payment.
The Welsh Government said "additional discretionary grants" and support for smaller businesses would also be available.
An £80m fund announced last week to help businesses develop in the longer term will be increased to £100m, with £20m ring-fenced for tourism and hospitality.
The latest number of confirmed cases of Coronavirus in Wales has been updated.
— Public Health Wales (@PublicHealthW) October 18, 2020
Mr Drakeford said he had written to Chancellor Rishi Sunak to ask for Welsh businesses to be given early access to the Job Support Scheme from Friday.
"That would remove the need for businesses to juggle the job retention scheme and the job support scheme during this fire-break period," Mr Drakeford said.
"Given the urgency, we have offered to pay the extra costs that will be involved in that from Welsh Government funds to help businesses retain staff.
"But it is only the UK Government that has the financial power to guarantee the levels of income support workers need."
Paul Davies, leader of the Welsh Conservatives, called on the Welsh Government to provide the evidence behind the "firebreak" and to go to the Welsh Parliament to answer questions.
"This is not a two-week break to solve the pandemic, it is likely that we will see regular lockdowns across the rest of the year," Mr Davies said.
"The Welsh Government must be clear what actions they are taking during the lockdown to prevent further Wales-wide lockdowns which will have a significant impact on people's lives and livelihoods."
Mr Davies said the lockdown was "not proportionate" and would heavily impact businesses in areas with low levels of Covid-19, such as Powys, Pembrokeshire and Ceredigion.