The leaders of Southwark and Lambeth councils have written to residents of their boroughs expressing concern over the recent rise in COVID-19 cases.
"Cases of coronavirus are rising across the country and in the last week we have seen a rise in cases here in Lambeth," said Cllr Jack Hopkins, leader of Lambeth Council, in an email to residents.
"While this has not been as large in our borough as in other parts of London and the country, it is of significant concern and means we all need to act with caution and have the welfare of our neighbours, friends and fellow Lambeth residents in our minds as we go about our daily business."
The most recently published seven-day case rate for Lambeth is 30 cases per 100,000 residents.
The threshold at which local measures are considered in England is 40 per 100,000.
Cllr Peter John, who this week steps down as Southwark's leader, used his valedictory newsletter to issue a similar warning.
He wrote: "I must tell you that the number of COVID-19 cases in Southwark has been increasing.
"Numbers are now rising across London and much of the country. We all need to help prevent the spread of the virus by following the rules."
On Tuesday morning Cllr John chaired his final meeting of the London Recovery Board, the capital-wide body set up to coordinate London's social and economic response to the pandemic.
Speaking at that meeting, Mayor of London Sadiq Khan said: "I think it's important I'm honest with you, which is that the numbers I have seen and the evidence I have is that I think we are about to embark on a second wave."
Earlier this month Southwark's acting director of public health set out a five-point plan to respond to the latest rise in COVID-19 cases.
At last week's annual public meeting, Guy's and St Thomas' medical director Dr Simon Stedden reported that in early September, SE1's hospitals had no COVID-19 patients in intensive care for the first time since March.
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