Government spokesman Yves Van Laethem during a briefing on 7 December told Belgians not to travel outside the country, including trips to the Netherlands, Germany and Luxembourg, citing high infection rates.

The Belgian government had previously told people not to travel to Luxembourg to shop while its businesses were closed during a partial lockdown in November. It reiterated on Monday that its residents should buy close to home.

The grand duchy itself has since adopted stricter measures aimed at containing the spread of Sars-CoV-2, closing down restaurants and other venues as well as limiting private gatherings.

“We know that at the moment Luxembourg is one of the countries with the highest rates of infection in Europe,” Van Laethem said, adding that “extremely frequent” cross-border exchange could be to blame for cases on the Belgian side of the border.

Van Laethem said there was currently no proof for this theory but that it should be examined further. Infections were up 19% over the past week in the Province du Luxembourg which borders the grand duchy.

Cases across the country were stable but still too high, he said. Among other reasons for high case numbers Van Laethem cited more frequent testing and schools reopening after the autumn holiday.

Luxembourg on the European Centre for Disease Prevention and Control (ECDC) virus map ranks worst in the EU at 1,197.4 infections per 100,000 inhabitants over the 14-day period ending 7 December.

Cases in Belgium are listed as 266.7 per 100,000 for the same time.

Belgium's finance minister Vincent Van Peteghem is scheduled for a visit to Luxembourg on 8 December for a meeting with Luxembourg's Pierre Gramegna (DP).

Luxembourg on Monday agreed with France to lift a cap on remote working days for cross-border workers until 31 March 2021. A similar deal could be up for discussion on Tuesday to allow people to work from home without facing taxation in their country of work and their place of residence.

The latest round of virus measures in Luxembourg came into effect on 26 November and prime minister Xavier Bettel (DP) on Friday said the government this week would begin preparing plans past 15 December, when the current restrictions are set to end.