Nigeria said on Wednesday it had confirmed its first cases of the Omicron COVID-19 variant, among them a sample from travellers who came to Nigeria in October, suggesting it had turned up weeks before it was reported in southern Africa.

"Retrospective sequencing of the previously confirmed cases among travellers to Nigeria also identified the Omicron variant among the sample collected in October 2021," Nigeria Centre for Disease Control (NCDC) said in a statement.

It did not give any details on the traveller.

First reported in southern Africa a week ago, Omicron has highlighted the disparity between massive vaccination pushes in rich nations and sparse inoculation in the developing world.

The NCDC said another two cases of the Omicron COVID-19 variant were from two travellers who arrived from South Africa last week.

"Given the highly likely increased transmissibility of the Omicron variant, it is imperative to put in place measures to curb community transmission," the NCDC said.

Data from other countries already shows the variant was circulating before it was officially identified in southern Africa and it has since been detected in more than a dozen countries. Work to establish if it is more infectious, deadly or evades vaccines will take weeks.

The announcement by the NCDC came ahead of a meeting between South African President Cyril Rampahosa and his Nigerian counterpart, Muhammadu Buhari, in Abuja on Wednesday, when Omicron is likely to be discussed.

Several nations have imposed travel restrictions on countries in southern Africa, which Ramaphosa says is unjustified and hurts developing nations.