The Paris-Roubaix one-day cycling classic is under threat again this year after the local authority said they were unsure the race could be run safely because of the Covid-19 pandemic.

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"I see the sky as less blue," the prefect of France's Nord region, Michel Lalande, told local radio on Monday.

Lalande expressed reservations about Belgian plans to allow their spring classics to go ahead.

"You will have to explain to me the coherence with social distancing rules and everything else," he said.

The focus of the cycling season shifts north this week for a series of annual one-day races in Belgium, northern France and the Netherlands.

These include three of cycling's five monuments starting with the Tour of Flanders in Belgium on April 4, Paris-Roubaix on April 11 and Liege-Bastogne-Liege in Belgium on April 25.

Paris-Roubaix, the 'Hell of the North', was not run last year. It was postponed in April because of the pandemic and rescheduled for October when it was called off again.