Scotland has advised against travel to virus hotspots in the north of England after new restrictions were imposed in several areas.
People in Greater Manchester, East Lancashire and parts of West Yorkshire are now banned from meeting others from different households indoors, following a rise in infections.
The Scottish government said citizens should only travel to these areas if "absolutely essential".
People already staying in the affected areas do not need to return to Scotland early but should monitor themselves for coronavirus symptoms.
First Minister Nicola Sturgeon said: "We have always been clear that localised flare-ups are likely as we continue to suppress the virus but by responding quickly and appropriately we can limit the effect these have on wider transmission.
"I strongly advise anyone planning to travel to areas affected in the north of England, or anyone planning to travel to Scotland from those same areas, to cancel their plans."
The R number has risen in England to between 0.8-0.9, while it is estimated to be between 0.8-1.1 in the North West.
Health Secretary Matt Hancock has told Sky News the new restrictions, which affect around four million people, are "absolutely necessary".
The order covers:
It means people in these areas will not be permitted to mix with other households (apart from those in their support bubbles) in private homes or gardens.
It is understood there is currently no endpoint to the restrictions but they will be subject to a weekly review.
Some exemptions will be put in place, including for the vulnerable.
The government will sign new regulations to make these changes legally enforceable.
The regulations will give local authorities and police forces the powers to enforce these restrictions and more details on these will be set out when the regulations are published.
Households may go to hospitality, for instance bars and pubs, but new guidance will make clear that two households should not go to hospitality together.
Mr Hancock said "households gathering and not abiding by the social distancing rules" was a reason for the decision, which had been taken to "keep the country safe".
Data shows that there has been less transmission in the area when people go to work or shops, he added.
"This is not the sort of decision anybody would want to take but as we've seen before it is important to move quickly," the health secretary said.
He also said his "heart goes out" to the Muslim community ahead of Eid celebrations, which will be heavily impacted by the new restrictions.
Labour leader Sir Keir Starmer criticised the way the announcement was made, branding it a "new low for the government's communications".
"No one would argue with putting in place local action to reduce the transmission of coronavirus," he tweeted.
"But announcing measures affecting potentially millions of people late at night on Twitter is a new low for the government's communications during this crisis."
There is disquiet too from backbench Conservatives over the handling of the announcement, with Hazel Grove MP Will Wragg tweeting: "Greater Manchester is not one homogeneous area. We must always err on the side of caution with COVID-19, but to treat all 10 boroughs the same is not the right approach."
Graham Brady, MP for Altrincham & Sale West, shared the post, adding: "I agree. Latest update for Trafford says 'infections continue to be at a low level'."
Out of the 19 local authority areas affected, the rate of COVID-19 in the seven days to 27 July has gone up in 13 of them, with 1,536 cases recorded in the space of a week.
Leicester's local lockdown was imposed at the end of June, but Labour's MPs for the area - Liz Kendall, Jonathan Ashworth and Claudia Webbe - said on Twitter that some restrictions there will now be lifted.
"The great news is our pubs, cafes, bars & restaurants can re-open and people can go on holiday with their own household," Ms Kendall tweeted.
"But leisure centres, gyms & pools still closed, and no meeting up with other households indoors."
The Department of Health later confirmed the restrictions will be eased from Monday.
Ms Webbe said Eid celebrations can take place at places of worship - provided social distancing is maintained - but not in private homes.
It has also been announced that from Saturday Luton will be brought in line with the rest of the country after "significant progress".
Greater Manchester mayor Andy Burnham told Sky News the "picture changed" in Greater Manchester over the last week and said the government was "right to take quick action".
He said the rise in cases "doesn't just relate to multi-generational households" but also a spike in cases amongst younger people.
Lisa Nandy, Labour's shadow foreign secretary whose Wigan constituency is affected by the restrictions, told Sky News the government "needs to be ready".
"They need to make sure that the guidance and clarity is there when they announce, not trickling out over Twitter and then hastily scrambling around to schedule a press conference," she said.