Details have emerged about the capsize of a migrant boat in the Mediterranean on Sunday that killed more than 800.

Prosecutors in Italy say the captain, who survived and faces multiple homicide charges, crashed the boat by mistake against a merchant rescue ship.

The capsize is the deadliest recorded in the Mediterranean, the UN says.

The International Organisation for Migration (IOM) says deaths in 2015 are 30 times higher than the same period last year and could rise to 30,000.