UK prime minister Boris Johnson on Saturday announced a raft of restrictions on travelers to contain the spread of the coronavirus following the confirmation of two cases of the new Omicron variant in the country earlier in the day.

Johnson, who was flanked by Sir Patrick Vallance and Professor Chris Whitty, his leading advisers during the pandemic, said the measures were "temporary and precautionary" and will be will be reviewed in three weeks.

The two PCR tests for all international travelers will be reinstated and all close contacts of positive Omicron cases must self-isolate for 10 days regardless of their vaccination status. Johnson said it appears that the Omicron variant spreads very quickly and can spread between two people who have been doubled vaccinated.

Additionally, the UK will require all arriving passengers to isolate until they can show a negative PCR test against COVID-19.

Johnson added that there will be a ramping up of mask wearing in shops and indoor settings, including public transport.

"There are many things that we just cannot know at this early stage," Johnson said.

"Right now this is the responsible course of action."

Despite fears over the discovery of the variant in the country, Johnson maintained the UK was in a much stronger position, largely due to the vaccine and booster rollout.

Meanwhile, the UK on Saturday reported 39,567 new confirmed COVID-19 cases and 131 related deaths in the latest 24-hour period, according to government figures.

This means the UK has now reported 10,110,408 confirmed cases and 144,724 related deaths since the pandemic began.

Separate figures published by the Office for National Statistics (ONS) indicated there have been 169,000 deaths registered in the UK where COVID-19 was mentioned on the death certificate.

Meanwhile, 19,933 people received a first dose of a COVID-19 vaccine while 23,149 others received a second dose taking the respective totals to 50,895,645 and 46,278,230.

A total of 351,195 people received a booster/third vaccine dose taking that total to 17,130,851.

Johnson said Health secretary Sajid Javid was in discussions with scientists to consider administering boosters to more people and reducing the gap from when an individual has their second dose.

According to Johnson, the Omicron variant diverges from previous configurations of the virus and reduces protection from vaccines over time.

(With input from agencies)