BRUSSELS -- Migrant deaths have risen to a record level on the Libya-to-Italy Mediterranean Sea smuggling route, and the increasing number of rescue boats trying to prevent mass drownings there might actually be helping the smugglers, the European Union's border and coast guard chief says.

Frontex Executive Director Fabrice Leggeri said Wednesday that authorities face a "sad paradox," for as the international community increases its efforts to send more rescue ships close to Libya, more people die as smuggling rings pack ever more people onto tiny dinghies and push them out toward the open sea.

He said the recorded number of migrant drowning deaths on the route in 2016, which might be much less than the true loss of life, stood at 4,579. Leggeri called it "tragic and the reasons are well known: the number of migrants now (arriving) on very small dinghies."

The Frontex report "Risk analysis for 2017" said smugglers have grown more bold and reckless, knowing that rescue boats will be right on the edge of Libya's territorial waters.

"Dangerous crossings on unseaworthy and overloaded vessels were organized with the main purpose of being detected" by military, EU or civilian vessels ready to pluck desperate migrants out of the water if necessary.

"Apparently, all parties involved in (search and rescue) operations in the Central Mediterranean unintentionally help criminals achieve their objectives at minimum cost, strengthen their business model by increasing the chances of success," the report said.

It said migrants and refugees setting off on the dangerous voyage were "aware of and rely on humanitarian assistance to reach the EU."

Leggeri said smugglers along the lawless Libyan coast put an average of about 100 people on a small boat in 2015 then increased that to 160 per boat last year. He said that, together with a decrease in food and survival equipment like life vests, it was a prime reason for the number of casualties.

Compared to the record number of deaths last year, the central Mediterranean route saw 2,869 deaths in 2015 and 3,161 in 2014. There is little sign the surge is abating, even during this winter. There were 228 recorded deaths in January, by far the biggest total for the month in recent years.

Overall, central Mediterranean migrant crossings increased 17 per cent last year to 181,459 people.

"This is and should be the focus we have to deal with," Leggeri said.