Travellers returning to the UK from Spain will have to quarantine for 14 days from Sunday, the BBC understands.
The UK government is expected to announce the change imminently, due to a significant spike in coronavirus cases in Spain.
It is believed the measures will come into effect in the early hours of Sunday.
Spain has warned a second wave could be imminent as cities including Madrid and Barcelona have seen cases surge.
The government of Catalonia has also said all nightclubs and late-night bars in the region are to close for the next two weeks due to a spike in infections.
The Spanish health ministry reported more than 900 new cases of the virus on Friday.
Quarantine measures for UK travellers were introduced in early June. But after pressure from the aviation and travel industries, the government and devolved administrations published lists of countries exempt from the rules.
Scottish First Minister Nicola Sturgeon tweeted that the decision was made after reviewing the latest data earlier on Saturday.
“This reinforces the point that these matters are subject to change at short notice and so my advice is to be cautious about non-essential foreign travel,” she said.
The new rules for Spain come a day after five other destinations were added to England’s quarantine-free list.
Anyone coming to England from Estonia, Latvia, Slovakia, Slovenia and St Vincent and the Grenadines will not have to isolate for two weeks on arrival, the government confirmed on Friday.
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