The IOM said the surviving migrants from the latest disaster spoke French, so probably came from West African nations such as Ivory Coast and Senegal.
"Because of the bad weather conditions, the two dinghies collapsed and the people fell at sea. Many drowned," IOM spokesman Flavio Di Giacomo said.
The organisation's spokesman in Geneva, Joel Millman, said information was coming in about other stricken boats, and warned that the overall toll "could easily triple by the end of the day".
Di Giacomo said the latest victims had left from a beach near Tripoli along with another dinghy also carrying more than 100 migrants plucked from their distressed boat by the Italian coastguard early on Monday.
Twenty-nine of them died of exposure in horrific conditions in international waters.
Humanitarian organisations said it was an avoidable tragedy.
Their small boat was hopelessly ill-equipped to cope with waves up to eight metres high, gale-force winds and torrential rain.
But doctors involved in the rescue operation believe more would have survived if they had been rescued by a large military vessel rather than the small patrol boats that were sent to their aid.
The UNHCR has blasted a new European Union-backed rescue patrol as ineffective for saving lives. The EU took over Mediterranean patrols after Italy phased out its robust Mare Nostrum operation, launched after 360 migrants died in 2013.
But the EU's Triton mission operates only a few nautical miles off Italy's coast, whereas Mare Nostrum patrols took Italian rescue ships up close to Libya's coast, where most of the smuggling operations originate.
"The Triton operation doesn't have as its principal mandate saving human lives, and thus cannot be the response that is urgently needed," Laurens Jolles, the head of the UNHCR for southern Europe, said in a statement.
- AFP, AP
