The UK has recorded 6,634 new coronavirus cases, the government has announced, making it the highest figure since mass testing began.
Another 40 people have died within 28 days of testing positive for the virus.
The latest figures take the overall number of confirmed cases to 416,363, and total deaths to 41,902.
Meanwhile, people arriving in the UK from Denmark, Slovakia, Iceland and the Caribbean island of Curacao now need to self-isolate for 14 days.
The rules take effect from 04:00 BST on Saturday.
The latest surge in cases comes after Chancellor Rishi Sunak announced plans aimed at stopping mass job cuts, and two days after Prime Minister Boris Johnson announced further restrictions to help curb the spread of coronavirus.
They include a 22:00 closing time for all pubs, restaurants and hospitality venues, which comes into force from Thursday. The sector will also be restricted by law to table service only.
The official records may show that the UK has just seen the highest number of new cases on a single day.
But it is, of course, nothing of the sort. At the peak of the pandemic in the spring we had such limited testing capacity that it was largely only hospital patients who were being checked.
It meant we were identifying just the tip of the iceberg.
Estimates have suggested there may have been as many 100,000 cases a day at the peak.
We are clearly not capturing all the infections – even now with the mass testing that is available.
Surveillance data last week suggested we may only be identifying around a half of cases.
But that still puts the infection levels well below what they were in the spring.
Hospital admissions and deaths have also started creeping up, but are still very low.
Health experts have been clear we are now on the upwards path so we should expect this trend to continue.
Crucial will be how quickly figures rise for all three measures, with the hospital cases and deaths the most important.
Evidence from Spain and France, which started seeing rises a few weeks before us, offer some hope.
Cases have been climbing gradually – at least more gradually than the trajectory government scientists warned could lead the UK to 50,000 cases a day by mid October.
Transport Secretary Grant Shapps said on Twitter that no countries would be added to the travel corridor list this week.
Singapore and Thailand were recently added to England and Scotland’s lists of safe countries.
The Department for Transport said the decision covers the whole of the UK and has been agreed with the devolved administrations.
Writing on Twitter, Mr Shapps said: “Data shows we need to remove Denmark, Slovakia, Iceland, and Curacao from the Travel Corridor list.”
He reminded passengers they were required by law to fill in a passenger locator form.
The form asks travellers to provide their contact details and UK address. Passengers can be fined up to £3,200 in England if they do not provide accurate contact details, or £1,920 in Wales.