A total of 336 people have died in the UK after testing positive for coronavirus - an increase of 55 since yesterday.
In England, 46 people died following a COVID-19 diagnosis, bringing the total to 303.
The Department of Health and Social Care says 6,650 people have tested positive for coronavirus across the UK as of 9am on Monday morning - an increase of 967 from the day before.
Scotland and Wales also reported another four deaths each, taking the totals to 14 and 16 respectively.
Northern Ireland reported one more death, taking its total to three.
Sunday's increase in deaths across the UK was 48.
Boris Johnson's daily afternoon briefing did not take place, but he will address the nation at 8.30pm.
It appears "much tougher" measures will be announced, said Sky's chief political correspondent Jon Craig.
The prime minister said yesterday he was considering tighter restrictions after thousands of people congregated in parks and tourist hotspots, going against advice to stay two metres (6.5ft) apart.
All British travellers abroad have also been advised by the Foreign Office to return to the UK immediately because "international travel is becoming highly limited".
MPs have today been debating the Coronavirus Bill to give authorities greater powers to stop the virus spreading.
It is being fast-tracked through parliament and is expected to become law by the end of this week.
The government is also looking at converting London's Excel Centre into a makeshift hospital with about 4,000 beds.
A team of military planners visited the exhibition venue over the weekend, the Ministry of Defence (MoD) said.
However, Sky News understands it would still be run by the NHS.
The Army will also help deliver protective equipment after health workers warned they did not have enough items such as masks and protective suits.
Train timetables have also been curtailed and carriage numbers reduced for the start of the new week.
However, many services into London remained full and people were pictured packing into Tube carriages.
The transport secretary tweeted that he plans to make some trains just for key workers so they have safe space.
In other moves, 1.5 million letters are being sent to elderly and vulnerable people ordering them to stay at home as part of a so-called "shielding" process.
Shops including Next and Greggs have become the latest to announce they are shutting all stores, after McDonald's took the same decision yesterday.
Pupils were also at home for the first day on Monday after schools and colleges shut until further notice on Friday.
Children whose parents are deemed key workers, such as NHS staff, have remained at school.