Migrants in Libya have been forced by smugglers to bury alive fellow migrants who are too sick or injured to board boats setting off across the Mediterranean towards Italy, it was revealed on Tuesday.

Migrants often spend months in Libya, held captive in squalid compounds or trying to earn enough money for their passage, and suffer knife and gunshot wounds at the hands of Libyan militia or ruthless gangs of traffickers.

They are even sold as cheap labour in modern-day slave markets, humanitarian organisations say. If they are too badly injured to walk to the beaches from where the rubber dinghies set out or if they are perceived as being too much trouble because of illness, then they are killed, said Flavio Di Giacomo, spokesman for the International Organisation for Migration.

“We have recently heard of cases where migrants who are wounded or sick have been buried alive by other migrants, on the orders of the traffickers,” Mr Di Giacomo told The Telegraph.