Paris, Feb 12 : The relentless spread of more infectious Covid-19 strains, detected in Britain, South Africa and Brazil, "particularly worries us," said French Health Minister Olivier Veran on Thursday. Currently, the variant first spotted in Britain represented up to 25 per cent of the total positive tests in France, up from 15 per cent a week ago, Veran said at a weekly press briefing on the epidemic situation, the Xinhua news agency reported. Meanwhile, 4-5 per cent of new cases were attributable to the variants detected in Brazil and South Africa, he said. Over the last four days, France has detected 300 cases of the variants -- first detected in South Africa and Brazil -- in the eastern French region of Moselle where "the situation is worrying," according to the minister. "We do not have at this stage an explanation of the spread of these variants," he said, noting that the new infections were not connected to clusters. Veran insisted that current restrictions to reduce social mixing "have already enabled us to slow the spread of the variant (first detected in Britain), and the virus in general," and for now there is no need for another nationwide lockdown. As of Thursday, France's cumulative number of confirmed Covid-19 cases had exceeded 3.4 million, after another 21,063 people tested positive in the past 24 hours, down from 25,387 registered on Wednesday. A further 360 Covid-19 patients had succumbed to the disease in one day, pushing the death toll to 80,803. In 24 hours, another 454 people were admitted to hospitals where a total of 27,007 patients are receiving treatment. Of those hospitalised, 3,337 are in intensive care units, up by 18, official data showed. As of Thursday, 2,135,333 first doses of vaccine (3.2 per cent of the total population) have been administered in France since the start of the vaccination campaign, according to the Health Ministry. As the world is struggling to contain the pandemic, vaccination is underway in some countries with the already-authorised coronavirus vaccines. Meanwhile, 242 candidate vaccines are still being developed worldwide -- 63 of them in clinical trials -- in countries including Germany, China, Russia, Britain and the United States, according to information released by the World Health Organization on February 9. /IANS