The European Union is grappling with a migrant crisis as hundreds of thousands of undocumented migrants, mainly from the Middle East and North Africa, arrive in EU member states, fleeing violence and poverty in their home countries.
Many of them use Bulgaria as a transit zone to enter the bloc and travel to wealthy EU states where they intend to apply for asylum.
Over 500,000 migrants and refugees have arrived in the European Union since the beginning of 2015, according to the European Commission.