Why is Mediterranean Sea so deadly for migrants?

Hundreds of people are feared to have drowned after a boat carrying up to 700 migrants capsized in the Mediterranean Sea, the Italian coastguard says.

Earlier this week, 400 people were feared to have drowned when their vessel capsized north of Libya.

And thousands of others perished trying to reach Europe in 2014.

BBC News looks at some of the reasons why it is such a deadly crossing - and what is driving migrants to take the risk.

Video produced by Sara Barman