Published: 2016-12-24 11:05:39 BdST
The latest figures, released by the UN's refugee agency, include 100 deaths reported on Thursday after two rubber dinghies sank off the coast of Italy.
This is the worst annual death toll ever seen, the agency said.
Just under 3,800 migrants died in the Mediterranean in 2015, according the International Organisation for Migration (IOM).
On average, 14 people have drowned in the Mediterranean every day this year despite an overall decline in the number of people making the crossing, according to the UN.
UNHCR spokesman William Spindler said the increase in deaths was "alarming" and the smugglers' practice of sending thousands of migrants off at a time made it difficult for rescuers of save them all.
The sharp increase in drowning deaths this year was due to bad weather, ever-flimsier, overladen boats and tactics to avoid detection, according to the UN.
Europe should organise legal ways for refugees to find safety, UNHCR said.
Most of the migrants have perished on the dangerous crossing from North Africa to Italy, after the shorter crossing from Turkey to Greece was closed off earlier this year under a controversial deal between Ankara and the European Union.
Almost 360,000 migrants entered Europe by sea this year, mostly arriving in Italy and Greece, according to the IOM.
Last year, when over a million people crossed the Mediterranean, 3,771 people drowned, UN figures showed.