Wales' capital city is facing a local lockdown as coronavirus cases rise "rapidly".
Cardiff council leader Huw Thomas has warned of potential restrictions on travel and different households mixing.
He told a virtual meeting of the authority that over the past seven days, the area has seen 38.2 cases per 100,000 people.
Mr Thomas said the city was on the verge of entering the Welsh Government's "red zone".
He said if that was to happen "then I fully expect that we will be implementing further restrictions as we have seen elsewhere" in south Wales.
Cardiff is home to 366,903 people and would be the seventh area to have tighter restrictions imposed.
People living in Caerphilly, Rhondda Cynon Taf, Bridgend, Blaenau Gwent, Merthyr Tydfil and Newport cannot leave their areas without a reasonable excuse.
Should Cardiff follow them into lockdown, it would mean more than a 1.2 million people - about a third of Wales' population - would be under tighter restrictions than the rest of the country.
Conservative councillor Jayne Cowan asked Mr Thomas if Cardiff would be put into a local lockdown in the next 48 hours.
He replied: "We'll look at the numbers again in the morning and make a decision based on that."
Mr Thomas said restrictions could be introduced "at speed" and could include a ban on households meeting or travel outside of Cardiff.
The council leader said the coronavirus test positivity rate stood at 3.8%, which exceeds the government's amber threshold of 2.5%.
There has been a sharp rise in hospital emergency attendance in the past week, he added, with the spread of infection "most frequently found within household settings".
Household mixing 'happening far too frequently'
"Our test trace and protect data suggests this is particularly in cases where family bubble rules have been breached, and also where people are mixing in indoor home settings and not following the rule of six," he said.
"The truth is that indoor mixing with people not in extended households in homes, cafes, bars and restaurants is happening far too frequently."
Mr Thomas said there had been a significant rise in those aged 35 to 50 testing positive.
Any new restrictions would need to be introduced by the Welsh Government.
Mr Thomas said he met First Minister Mark Drakeford and Health Minister Vaughan Gething prior to Thursday night's council meeting.
The threshold for foreign countries to be added to the list of destinations where people need to quarantine for 14 days upon arrival in the UK is 20 cases per 100,000.
'Businesses won't survive'
Cardiff councillor Jayne Cowan told BBC Radio Wales a local lockdown was "inevitable" but feared the impact on businesses.
"Many businesses won't survive another lockdown," she said.
"We're seeing many thousands of cases of people having livelihoods stripped away. As part of the first lockdown, I was made redundant from my part time job.
"The Welsh Government needs to come up with the goods."
Welsh Conservative health spokesman, Andrew RT Davies, tweeted that a "it's incumbent on the Welsh Labour government to bring forward a package of financial support for the many businesses (particularly hospitality) that will be devastated by the news".
He said a blanket lockdown of the city "really isn't local".
Rhun ap Iorwerth, Plaid Cymru health spokesman, said: "Shutting pubs slightly earlier isn't going to be enough - the Welsh Government must think of a suite of new steps, which are perhaps stricter but for a shorter period, in order to control these new spikes."