LONDON -- British Health Secretary Matt Hancock on Sunday raised the prospect that London could be under lockdown for months as he has warned it will be "very difficult" to keep a virulent new strain of the coronavirus under control until vaccinations are rolled out.

His remarks came as he was speaking to Sky News just hours after the new Tier Four restrictions came into force in the British capital and parts of southeast England.

The new tighter restrictions will be reviewed on Dec 30, 2020. However, the health secretary indicated it was unlikely they would be relaxed at that point.

"It is going to be very difficult to keep it under control until we have the vaccine rolled out," he said. "We know with this new variant you can catch it more easily from a small amount of the virus being present."

"All of the different measures we have in place, we need more of them to control the spread of the new variant than we did to control the spread of the old variant," he said. "That is the fundamental problem."

On Saturday, British Prime Minister Boris Johnson announced the new Tier Four of coronavirus restrictions for London and other parts of England to combat an alarming surge in infections linked to a new virulent strain.

From Sunday morning, London, the South East and East of England will move into Tier Four restrictions, which will be broadly similar to national restrictions introduced in England in November, Johnson announced at a virtual press conference at Downing Street.

The prime minister said the latest infections in parts of England are "being driven by the new variant of the virus".

"New variant may be up to 70 percent more transmissible," he said.

England was previously under a three-tier system. London and parts of Essex and Hertfordshire had just moved into Tier Three on Wednesday while some other areas in east and southeast of England entered Tier Three from Saturday following a rapid rise in infections in the area.

To bring life back to normal, countries such as Britain, China, Germany, Russia and the United States are racing against time to develop coronavirus vaccines.