France has reported its first case of the new Omicron coronavirus variant near Paris as the government's top scientific adviser says it could become dominant in the country by the end of January, reports Reuters.

The health body for the Ile de France region of greater Paris said in a statement an Omicron case had been found in a person who returned from Nigeria. This followed a case found in the French Indian Ocean island of La Reunion last month.

Jean-Francois Delfraissy told BFM television the "true enemy" for now was still Delta, spreading in a fifth wave.

"We should see a progressive rise of the Omicron variant, which will take over from Delta," possibly by the end of January, he said.