Health officials have urged people to stop ignoring advice on social distancing as they battle to slow the spread of coronavirus.
It came as many appeared still not to be heeding warnings about taking the most basic precautions.
Images showed hundreds of people going about their daily lives in central Belfast on Friday.
In other areas there were reports of coffee shops and cafes being busy with customers.
Prime Minister Boris Johnson has announced the closure of cafes, pubs and restaurants in a bid to tackle the pandemic.
He urged people: "For now, at least physically, we need to keep people apart."
And he added: "The more effectively we follow the advice we are given, the faster this country will stage both a medical and an economic recovery in full."
First Minister Arlene Foster said putting an end to socialising will help prevent deaths.
The DUP leader told BBC's Inside Politics: "This is a way of dealing with this disease and bringing down those numbers of deaths.
"This is for the community's protection, it is for our elderly and we are asking everyone to come together to embrace the giant spirit and the spirit of Northern Ireland."
It came less than 24 hours after a dire warning about the potential loss of life if the virus spread is not reduced.
Health Minister Robin Swann said that unless everyone follows the guidelines, up to 15,000 people could die as a result of Covid-19.
Officials have been urging people to avoid all large gatherings and gatherings in smaller public spaces such as pubs, cinemas, restaurants, theatres, bars, and nightclubs.
Dr Hugo Van Woerden of the Public Health Agency said: "I cannot emphasise enough how important it is to practise social distancing as a key step in saving lives.
"The guidance to socially distance ourselves from others applies to everyone.
"We should all be taking steps to reduce social interaction between people in order to reduce the transmission of coronavirus.
"Every one of us has a role to play in this battle."
On Friday the police was forced to issue a warning to school leavers to avoid the traditional end of term gatherings.
"Anyone considering attending an end of school party, please consider your own health and the health of others. Social distancing is vital to combat the spread of Covid-19," the PSNI said.
In other parts of Northern Ireland some continued to ignore the advice.
While most cafes, restaurants and pubs in Londonderry adhered to government recommendations, in neighbouring towns of Coleraine, Portrush and Portstewart, for some it was business as normal.
Serving staff in bars, cafes and restaurants cannot keep two metres from members of the public while carrying out their job and remain safe, which helped many owners make the decision to shut up shop.
Derry City Centre manager Jim Roddy said: "Some businesses including restaurants are being imaginative and have adjusted their businesses in ways that don't put their staff or the public at risk and keep to the principles of safe distancing."
A spokeswoman for the Causeway Chamber of Commerce said its members were looking to the Government for clarity on the issue of opening.
She said: "Council has no power to direct premises to close or enforce social distancing.
"It is the responsibility of everyone to follow the relevant guidance and once again we would urge everyone to play their part in the fight against Covid-19."
A leading retail chief called on the public to follow the clear guidelines "as lives depend on it".
Retail NI's Glyn Roberts also called on the Executive to set up a single Covid-19-related website and social media channel to make sure the right messages are getting across to the public.
"It's been made very, very clear that we all need to follow the advice," he said. "We simply have to. Lives depend on it and that message has to get through.
"That's why Retail NI will be asking the Executive to set up a specific website and social media channel to make sure the correct and relevant advice is there for all.
"At the minute advice is coming from all different departments and there's so much out there that's irrelevant or wrong. We need a single coordinated platform that people can trust. We're really seeing the benefit social media can have in getting information across, but it needs to be from a single, coordinated source.
"We really have to follow to the letter what the advice is. We have those who are working in the retail trade, the people serving us in shops to think of as well.
"They are providing an invaluable service by remaining open and we owe it to them all to abide by the rules as much as we possibly can."
The Public Health Agency also warned of the threat posed by Covid-19 if the social distancing guidelines are not followed.
Dr Van Woerden said: "We understand that this will be difficult, particularly with Mother's Day this weekend for example, so it is worth looking at keeping in touch using your phone, the internet and social media.
"If you are outdoors, stay more than two metres away from others.
"As part of the effort to reduce the spread, only use the phone or online facilities to contact your GP or other essential services.
"We strongly advise you to follow the measures as much as you can and to significantly limit your face-to-face interaction with friends and family if possible, particularly if you are over 70, have an underlying health condition or are pregnant."
Scientists said social measures will need to be in place for most of a year at least in order to control the spread of Covid-19.
The Scientific Pandemic Influenza Group on Modelling agreed on Monday that, while the severity of measures could alternate during the period, "stricter" measures would need to be enforced for at least half of the year to keep cases at a level the NHS can cope with.