EU countries accused of holding migrants in 'black sites'

Security forces along several EU borders in Bulgaria, Hungary and Croatia are using so-called "black sites" - secret facilities used to imprison refugees unofficially.

Asylum seekers said they were kept in a cage in the yard of Sredets border guard station in Bulgaria, where some refugees reported being beaten and abused before being pushed back to neighbouring countries.

A joint investigation with Lighthouse, Sky News and European partners has obtained the first visual evidence of these sites.