Extra restrictions on social gatherings are to be imposed across Northern Ireland, First Minister Arlene Foster has said.
There will be no mixing of two households indoors, except for single-person bubbles and certain other exemptions, from 6pm on Tuesday.
No more than six people from two households can meet in private gardens.
Ms Foster said: “These are limited restrictions which I hope by taking action at this early stage means we can prevent the need for more draconian measures.”
The evidence shows most community transmission of the virus is due to people visiting other households.
The DUP leader said: “It is in an environment where we feel safe and relaxed that we drop our guard.
“The mixing of households indoors provides one of the best opportunities for the spread of the virus.”
House parties in south Belfast’s student Holyland district and a pitch invasion by Gaelic Athletic Association sports fans have caused concern over recent days.
The First Minister said some people had lost the run of themselves as she warned them to comply with the restrictions.
Mrs Foster said: “Whether they ran onto the pitch at a GAA match, partied in bars afterwards, swarmed the streets of Belfast Holyland or indeed crowded into house parties, that kind of behaviour isn’t just a risk to those present, but of course for everyone they subsequently come into contact with.”
The DUP leader said a Stormont enforcement group was examining how to clamp down on such behaviour going forward.
“I’m putting you on notice that we intend to take this matter very seriously,” she said.
Between 2% and 4% of tests overall are now positive and show increased community transmission, Stormont’s chief scientific adviser Professor Ian Young said.
The reproductive rate of the virus has risen to 1.4 and in some local districts would be about two, the expert said.
In the last 48 hours, nearly 400 new cases were reported and “substantial” increases have happened across Northern Ireland, the First Minister said.
Previously, the limitations were applied to greater Belfast and Ballymena in Co Antrim.
Mrs Foster said: “This is not returning to lock down.
“Doing nothing was not an option but neither is returning to full lockdown.”
Professor Young said it had been possible to put in safety measures at hospitality outlets which did not exist in private homes.
Pubs which do not serve food will open on Wednesday.
The chief scientific adviser said: “The virus is everywhere and will spread everywhere, and hence our advice is that generalised restrictions are required.
“We believe this is a proportionate response to the increased number of cases, focusing on the settings where most cases seem to be acquired at present.”
Deputy First Minister Michelle O’Neill said people were “fed up and tired” with Covid-19, but it posed a real threat and they had the opportunity to prevent an even more challenging situation this winter.
She said: “Covid-19 has been allowed to get a foothold in our community and we need to take action now.
“This is a fightback – the months ahead will be difficult.”
Two more Covid-linked deaths were reported in Northern Ireland over the weekend, the Department of Health has said.
The death toll in the region recorded by the department now stands at 577.
There were also a further 125 new confirmed cases of the virus in Northern Ireland in the last 24-hour reporting period.