Catalonia's sacked separatist leader Carles Puigdemont and four of his former ministers were released with conditions in Belgium on Sunday after turning themselves in to face a Spanish warrant for their arrest.
Under the Belgian political system, major international deals need to be signed off by regional parliaments.
Russia’s Foreign Ministry said in a statement that it has presented Alex Van Meeuwen, Belgium’s ambassador in Moscow, with evidence proving the involvement of Belgian Air Force jets in a recent airstrike on a Syrian village that killed four civilians.
Countries across Europe are strengthening security following the Nice terror attack which claimed the lives of at least 84 people. It comes as France extends its state of emergency for an additional three months.
Thursday’s referendum was a close contest: 52% backed leaving and 48% voted to remain.