COVID surge testing is to be carried out in parts of Wandsworth, southwest London, after cases of the South African variant were identified.
The Department of Health and Social Care (DHSC) said additional testing and genomic sequencing is being deployed within the SW11 and SW15 postcodes.
Enhanced contact tracing, where tracers look back over an extended period to determine the route of transmission, will be used for individuals testing positive with a variant of concern.
Residents living within the targeted areas are strongly encouraged to take a COVID-19 test when offered, whether they are showing symptoms or not.
People with coronavirus symptoms should book a free test online or by phone so they can get tested at a testing site or have a testing kit sent to them at home.
The extra testing is being introduced in addition to existing extensive testing and will help to monitor and suppress the spread of the virus, the DHSC said.
Any positive cases found will be sequenced for genomic data to help increase understanding of coronavirus variants and their spread.
As the South Africa variant shares the same mutation believed to be responsible for increased transmissibility in the Kent variant, it will follow that it shares traits with it.
This includes being up to 70% more transmissible.
Surge testing is also being carried out in the nearby SW8 and SW9 postcodes in Lambeth.
Elsewhere in the capital, there is such testing in Barnet (specific areas within N2 and NW4), Brent (specific areas within North Wembley), Croydon (specific areas in the CR0 postcode and specific areas within South Norwood and Thornton Heath), and Redbridge (Loxford and Clementswood wards).
Also having extra testing is South Gloucestershire (within the following postcodes: BS32 0, BS32 8, BS32 9, BS34 5 and BS34 6), and Stafford District.
Meanwhile, the UK has recorded a further 190 coronavirus deaths and 5,926 cases in the latest 24-hour period.
The government said the latest figures mean the number of people who have died within 28 days of testing positive for COVID-19 in the UK stands at 124,987.
The number of coronavirus deaths reported on Wednesday is lower than Tuesday's count of 231, although there was a rise in cases from the figure of 5,766.
More than 22.8 million Britons have now had a first vaccine dose.
Watch: Boris Johnson rejects EU claim that UK has imposed vaccine export ban