London will move into England's highest tier of COVID-19 restrictions, the government said on Monday, citing increased infection rates that may be partly linked to a new variant of the coronavirus.

UK Health Secretary Matt Hancock said more than 1,000 cases of the new variant had been identified, mainly in southeastern England.

Although there was currently nothing to suggest the new strain was likely to cause more serious disease or that it would not respond to a vaccine, Hancock said that it could be contributing to higher infection rates.