Nicola Sturgeon said images of packed pubs made her "want to cry" as she urged people to be cautious while socialising to keep coronavirus at bay.
The Scottish first minister announced there had been no new deaths in Scotland from Covid-19 for the eighteenth day running but said she would not shy away from reimposing restrictions if cases began to spike again.
"Across the county and across social media we are seeing evidence of people - and it is largely younger people - gathering together with little or no physical distancing in place," she said.
"I've seen pictures on social media over this weekend that, not to put too fine a point on it, made me want to cry looking at them."
Speaking at the Scottish Government's coronavirus briefing on Monday she announced that 11 new cases had been recorded in Aberdeen, where an localised outbreak has been detected.
While Ms Sturgeon said she could not yet say if those cases were linked to the ongoing situation, she warned that cluster was "exactly what we feared when we reopened hospitality".
SNP MP Stephen Flynn had previously posted two photos of Aberdeen city centre on at the weekend on social media, stating that he was "scunnered" by the images showing large numbers of people queueing for pubs and bars.
The first minister warned that it was likely that there would be more Covid-19 clusters in Scotland "in the weeks ahead".
At a UK level chief medical officer Chris Whitty warned last week that Britain had "probably reached near the limit or limits" of which sectors of the economy could be opened up without seeing the virus return in earnest.
England still has a significantly higher levels of Covid-19 infection than Scotland, with eight recorded deaths across the UK as a whole according to the latest figures.
Academics have since warned that this might mean pubs could need to shut to allow for a return of schools in September.
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