Nicola Sturgeon said more parts of Scotland are showing worrying signs of rising infections as she confirmed weekly coronavirus restrictions.
The alarm was raised in two regions, Perthshire and Clackmannanshire, despite claims of "cautious optimism" that lockdown is working nationally.
It comes as daily infection figures dropped to 771 across Scotland and one week after 11 councils, including Glasgow, were ordered into the highest level 4 alert.
At Holyrood, Sturgeon said: "The latest data shows that across the country and in most local authority areas the restrictions in place are having an impact.
"The number of new cases across the country has stabilised in recent weeks. But we now have grounds for cautious optimism the numbers may be declining.
"There is also evidence admissions to hospital and ICU are declining now too, though it is important to note these figures tend to fluctuate on a day-to-day basis."
Sturgeon said the rate of infection, known as the R number, is between 1 and 0.8. This is an important signal in how the virus is spreading. It needs to be below 1 to show the rate is slowing down.
There are regional variations which led to the big difference between west central Scotland and the rest of the country.
Confirming the levels for another week, Sturgeon said all areas except East Lothian will continue with the same restrictions. But she highlighted two for attention.
"We are monitoring Clackmannanshire, and Perth and Kinross, particularly carefully given recent increases in cases in these areas," Sturgeon said.
Both areas are already in level 3. A move to level 4 would see non-essential shops shut and hospitality closed even in the rural north of Perthshire.
Sturgeon confirmed Orkney, Western Isles, Shetland and Highland stay at level 1 where infections are low.
Dumfries and Galloway, and Argyll and Bute, are still at level 2 but could go down to level 1 soon.
Increases in infections in Aberdeenshire and Aberdeen city have been blamed on isolated outbreaks and will not lead to tighter rules, Sturgeon said.
East Lothian moves to level 2, allowing for more freedom in pubs and restaurants. It is the only council area moving to a different tier of restrictions this week.
Earlier, Sturgeon confirmed a blow for Midlothian which had been told to expect a move to lighter level 2 until last night when a spike in infections forced a rethink.
