The European Commission expressed its astonishment Monday following a decision by Belgian authorities to prolong a ban on all non-essential travel as part of measures to combat the coronavirus pandemic.

The EU’s executive arm had previously warned six member states including Belgium that their travel-limiting measures aimed at slowing down the pace of new infections could undermine the principle of free travel within the 27-member bloc and the single market.

“We have received answers to our letters to member states, from Germany, Belgium and Finland,” said Christian Wigand, the commission spokesman in charge of justice, equality and rule of law. “As far as Belgium is concerned, we have been surprised to read in the press a new prolongation of the ban on travel on Friday, while it was not mentioned in the letter to the commission we received the day before.”

Prime Minister Alexander De Croo’s government introduced the ban at the end of January, first extended it until April 1 and further extended it last week until April 18 to cover the next school holidays.

Under the Schengen Code, member states can introduce border checks at their internal borders on grounds of a serious threat to internal security, but the Belgian ban goes well beyond the EU’s recommendations for a common approach to travel measures during the pandemic. The commission’s stance is that nonessential travel should only be discouraged.

“The commission’s position has not changed and is very clear,” Wigand said, insisting that restrictions should be proportionate. “We don’t believe that a ban on travel respects that principle and we have asked Belgium to replace it with more targeted measures.”

Belgium, the center of European institutions and decision-making at European level, represents a major crossroads, sharing borders with France, Germany, Luxembourg and the Netherlands. The country of 11.5 million has been badly hit by the pandemic, with more than 22,000 deaths related to the virus recorded so far. The Belgian government considers the ban a crucial element of its strategy to avoid another surge of infections as the current numbers seem to plateau.

In addition to the letters sent to Germany, Belgium and Finland, the commission also wrote to Denmark, Hungary and Sweden.

“Our goal remains to find solutions as quickly as possible to guarantee the functioning of the single market and respect of European rights related to free movement,” Wigand told journalists. “We will analyze answers from the respective member states and examine quickly all options on the table.”

Wigand did not elaborate but the EU could decide to start proceedings for breach of EU laws that could eventually lead to sanctions against the six countries.