Belgium and the Czech Republic have called for new European Union sanctions to counter Russian influence in the upcoming European elections after several countries discovered early interference, an open letter to the EU leadership showed.

The letter, dated April 16 and signed by Belgian Prime Minister Alexander de Croo and Czech President Peter Fiala, was addressed to the heads of the European Commission, the Council and the European Parliament.

The two leaders say instances of pro-Russian disinformation and interference had already been found in several member states. In particular, Belgian security services unearthed a network inside Belgium that involved cash transfers that took place in part in the Czech Republic.

The network aimed to forge cooperation between pro-Russian politicians at the European Parliament, help elect more pro-Russian candidates and appoint “people active within this network as employees (of newly elected) MEPs (members of parliament).”