There is a high threat from terrorism. Attacks could be indiscriminate, including on public transport and transport hubs and in places frequented by foreigners.
Brussels hosts a number of international institutions (EU, NATO and Supreme Headquarters Allied Powers Europe (SHAPE)) and government and foreign embassy buildings which are sensitive locations.
There is considered to be a heightened threat of terrorist attack globally against UK interests and British nationals, from groups or individuals motivated by the conflict in Iraq and Syria. You should be vigilant at this time.