The grim new statistic followed the deaths of some 800 people on Sunday when a boat packed with migrants capsized near Libya in the deadliest Mediterranean shipping disaster for decades.
"IOM calculates the 2015 death toll now is more than 30 times last year's total at this date . . . when just 56 deaths of migrants had been reported on the Mediterranean," spokesman Joel Millman told reporters in Geneva.
"IOM now fears the 2014 total of 3,279 migrant (deaths) on the Mediterranean may be surpassed this year in a matter of weeks, and could well top 30,000 by the end of the year, based on the current death toll," he said.
UNHCR spokesman Adrian Edwards said Sunday's migrant boat tragedy was "the deadliest incident in the Mediterranean we have ever recorded."
Edwards said there had been 1,300 deaths in April alone, making it the deadliest month on record.
The IOM spokesman said traffickers were increasingly packing in more people on overcrowded vessels, thereby greatly adding to the risk factor.
"The way we see it is that if there were 800 people on that fishing boat that sank . . . we can imagine that the same boat last year would have had 200 people on it," Millman said.
"If there's a real shortage of crafts they're going to do these reckless things," he said.
"If that's the case, and it appears to be, there is no reason not to be afraid that death rates could soar astronomically, because they are taking these measures to move people."
Volker Turk, the director of international protection at the UN refugee agency, said most of the migrants taking the perilous journey were refugees.
"If you look at the numbers last year, over 50 percent of the people who crossed the Mediterranean were people in need of international protection — mostly Syrians, Eritreans, some Somalis," he said.
Italy, one of the frontline European states for illegal immigration, suspended its Mare Nostrum search-and-rescue operation late last year in protest over its rising cost.
That was replaced by a smaller and much more restricted EU-led mission called Triton.
"With the end of Mare Nostrum, we indeed unfortunately predicted the types of scenarios that are playing out today, and we hope that the European council meeting on Thursday will give adequate attention to the search and rescue dimension of this issue," Turk said.