Boris Johnson issued a warning about a new coronavirus variant from Brazil and said the government are looking at tough measures to stop it entering the UK.
The new Covid variant was detected in Japan in four travellers arriving from Brazil.
Japanese authorities discovered it shares a mutation with the highly infectious variants found in the UK and South Africa.
In his two-hour questioning from a committee of MPs, the Prime Minister also acknowledged concerns about the new strain of coronavirus from Brazil, but stopped short of promising a travel ban on the South American country.
He said: "We already have tough measures to protect this country from new infections coming in from abroad.
"We are taking steps to do that in respect of the Brazilian variant."
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This morning Safeguarding Minister Victoria Atkins said the UK was monitoring the new Brazilian coronavirus variant "very carefully" and that "practical measures" were being worked on.
Speaking on Sky News, she said: "This variant has been spotted and it is not unusual for viruses to develop variations in their strains.
"But in terms of the UK, we are monitoring it very, very carefully, we have a world-leading team of scientists working on the different forms of the virus.
"And as the Prime Minister said yesterday, in terms of practical measures, they are being worked on at the moment and no doubt we will hear more in due course as to measures to help deal with that."
When the South African variant was discovered the UK imposed a ban on direct flights from South Africa and restrictions on flights to the country.
Anyone who had travelled there recently, and anyone they have been in contact with, were told to quarantine immediately.
