The UK's travel restrictions have been criticised by Nigeria, after the country was placed on the red list amid fears over the Omicron variant.
"What is expected is a global approach, not selective," Sarafa Tunji Isola, Nigeria's high commissioner to the UK, told the BBC on Monday.
He also echoed comments made by the UN's chief, who described restrictions imposed on some southern African countries as "travel apartheid".
New rules came into force at 04:00 GMT.
It means travellers arriving from Nigeria will be required to enter hotel quarantine - at their own expense - and isolate for 10 days.
"The travel ban is apartheid in the sense that we are not dealing with an endemic," Mr Isola told the Today programme. "We are dealing with a pandemic. Whenever we have a challenge there must be collaboration."
UK government minister Kit Malthouse, meanwhile, said the wording "travel apartheid" was "very unfortunate language".
"We understand the difficulties that's created by these travel restrictions, but we're trying to buy a little bit of time so that our scientists can work on the virus and assess how difficult it's going to be" he told the BBC.
The UK's Department of Health and Social Care said all countries collect data differently, meaning it is hard to directly compare the information. It said the government would continue to keep the data under review.
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Nigeria became the 11th country to go on the UK's red list for international travel on Monday. All nations currently on that list are African.
The only people allowed to enter the UK from these countries are UK or Irish nationals, or UK residents. They will have to pay for and self-isolate in a pre-booked government-approved hotel for 10 days.
UN Secretary General António Guterres first used the term "travel apartheid" on Wednesday, telling reporters in New York that bans "are not only deeply unfair and punitive, they are ineffective".
Ghanaian President Nana Akufo-Addo has also condemned the restrictions on African countries, describing them at a press conference last week as "instruments of immigration control".
A UK government statement on Saturday announcing Nigeria's addition to the red list said the "vast majority" of Omicron variant cases in the UK "have clear links to overseas travel from South Africa and Nigeria". In the last week 21 Omicron infections had been reported in England that "originated from Nigeria", it said.
Nigeria reported its first Omicron cases last week, the first country in west Africa to record an infection of the variant. In total, the country has reported 214,622 cases of coronavirus since the pandemic began, according to John Hopkins University data.
The new variant was first detected in South Africa in November. Little is yet known about it, but there are concerns it could be more transmissible, with early data suggesting it may evade some of our immunity to Covid.
On Friday, World Health Organization (WHO) top scientist Soumya Swaminathan said Omicron could become the dominant strain worldwide, although she cautioned that this is hard to predict and urged people not to panic.