Britain on Friday "put the brakes on" easing lockdown measures and imposed new rules on millions of households in northern England, following concerns over a spike in coronavirus infections.
The reopening of high-risk activities such as casinos, bowling alleys and skating rinks, which was meant to begin on Saturday, will be delayed until at least August 15, as will the reintroduction of indoor performances and pilot schemes of larger crowds at sporting events, Boris Johnson announced.
"I have said our plan to reopen society and the economy is conditional.. that we would not hesitate to put the brakes on if required. Our assessment is that we should now squeeze that brake pedal," the Prime Minister said in a Downing Street briefing.
Johnson, who earlier this week warned of a "second wave" of cases in Europe, added that Britain "cannot be complacent" about increasing infection numbers.
His announcement came hours after the government increased regional lockdown measures -- under which people from different households are banned from meeting indoors -- for some four million people across Greater Manchester and parts of Lancashire and Yorkshire.
Health Secretary Matt Hancock said the restrictions were being brought in because people were "meeting and not abiding to social distancing".
"We take this action with a heavy heart, but we can see increasing rates of Covid across Europe and are determined to do whatever is necessary to keep people safe," Hancock said on Twitter.
Government data released Friday showed there was "some evidence that the incidence of new infections has increased in recent weeks" in England.
However, Chief Medical Officer Chris Whitty said "I don't think it is helpful" to talk yet of a second wave sweeping across Europe.
The local measures came into effect at midnight (2300 GMT Thursday), just hours after being announced.
Andy Burnham, the mayor of Manchester, backed the measures due to an increase in infections.
"The picture in Greater Manchester has changed over the last seven days," he told the BBC.
"We have a rise in nine out of the 10 boroughs, the reality on the ground is changing."
But the new measures have come under criticism from the opposition Labour party for being announced late at night.
Labour leader Keir Starmer said on Twitter: "Announcing measures affecting potentially millions of people late at night on Twitter is a new low for the government's communications during this crisis."
They also come into force just as celebrations of the Muslim festival Eid al-Adha begin. Areas affected by the latest lockdown have significant Muslim populations.
Scottish First Minister Nicola Sturgeon warned her citizens against travelling to the affected areas.
"To... minimise risks of onward transmission here, @scotgov is STRONGLY advising against non essential travel between Scotland and these parts of the north of England," she wrote on Twitter.
Hancock said Leicester would now follow the same ban on meetings between different households being applied to Manchester and parts of West Yorkshire and East Lancashire.
Britain's official virus death toll stands at 45,999 but is believed to be as high as 65,000 if excess deaths are used as a guide.