Cardiff could face tougher local restrictions after the number of coronavirus cases in the Welsh capital "accelerated rapidly", officials have said.
Cardiff Council leader Huw Thomas said the city was "yet" to face local lockdown measures but had seen 38.2 cases of Covid-19 per 100,000 people over the past five days.
Over the past seven days, Cardiff reached a test positivity rate of 3.8 per cent, exceeding the Welsh Government's "amber" threshold of 2.5 per cent.
The city has a "traffic light roadmap" strategy for managing the pandemic.
Cllr Thomas said on Thursday: "This has meant that over the past week Cardiff has moved from a relatively stable position to one where the city is on the verge of entering the Welsh Government's 'red zone'."
He added: "As we have seen over the past week, the situation can change quickly.
"If case numbers continue to rise over the weekend there is a very real possibility that Cardiff will enter into the Welsh Government's 'red zone'.
"If that were to happen then I fully expect that we will be proposing further restrictions."
Local lockdown restrictions are in place in six areas of Wales, including in Newport.
For example in Bridgend County Borough, people are now not allowed to leave or enter the area without a reasonable excuse, or meet people indoors without a good reason.
The warning comes after it was announced that pub-goers in Wales will be given an extra 20 minutes to finish their drinks after last orders, with the country's new 10pm cut-off for alcohol sales now in force.
From 6pm on Thursday, changes to coronavirus regulations mean Welsh hospitality businesses including pubs, cafes, restaurants, sports clubs and casinos must not supply alcohol between 10pm and 6am the following day.
Licensed premises will only be able to provide table service for customers when consuming food or drink, and following a 20-minute period to allow customers to finish their drinks at 10pm, must close by 10.20pm.
Read More
The new rules differ from those coming into force in England, where from Thursday all pubs, bars and restaurants must shut by 10pm - meaning last orders will come sooner than for those drinking in Wales.
The Welsh Government is allowing cinemas which sell alcohol to close later than 10.20pm for the purpose of concluding the showing of a film.
But the 10pm cut-off will also apply to off-licences, including supermarkets, and deliveries of alcohol such as through a home delivery app.
On Wednesday, First Minister Mark Drakeford said licensed premises would not be required to close immediately at 10pm as in England following representations from those in the industry.
On Thursday, Public Health Wales said there have been a further 348 cases of Covid-19 in Wales, bringing the total number of confirmed cases in the country to 21,896.
One further death was also reported, with the total number of deaths since the beginning of the pandemic increasing to 1,606.
