Residents aged 16 and over in eight areas across Surrey, London, Kent, Hertfordshire, Southport and Walsall are being asked to take tests, regardless of symptoms.
The health secretary said the UK must come down "hard" on the variant .
Previous cases in the UK were connected to South Africa.
But random checks found 11 cases that could not be linked to international travel.
Matt Hancock told a Downing Street news conference on Monday that there was "currently no evidence" to suggest the South African variant was "any more severe, but we need to come down on it hard, and we will".
The neighbourhoods being targeted for testing are:
- W7, N17 and CR4 in London
- WS2 in Walsall
- ME15 in Maidstone, Kent
- PR9 in Southport
- EN10 in Broxbourne, Hertfordshire
- GU21 in Woking
Cred: Nick Triggle, BBC Health Correspondent