At least 239 people, assumed to be from West Africa, lost their lives in two shipwrecks off the coast of Libya, the UN's International Organisation for Migration (IOM) said on Thursday.
A group of refugees, including 20 women and six children set off in a rubber dinghy from Libya at around 3am on Wednesday, but after a few hours, their vessel collapsed according to the IOM's Flavio di Giacomo, who had cited accounts by survivors.
Most of the refugees had drowned before rescue crews had arrived.
Twelve bodies, including three babies, were recovered, while 27 survived the tragedy.
At around the same time, another vessel carrying 130 people had sunk.
Two female survivors reported the incident after they were rescued.
IOM said 4,220 lives had been lost in the Mediterranean Sea so far this year, while 3,777 were lost in 2015.
October saw a surge in refugee arrivals in Italy, with 27,388 arriving, more than the two previous Octobers combined, and bringing this year's total arrivals to over 158,000, di Giacomo said.
The smugglers who arrange the journeys have told refugees that European training of Libyan coastguards means the rescue missions will soon be handed over to Libya and any rescued refugees will be taken ashore in Libya rather than Italy, di Giacomo added.
This was possibly causing a rush to board boats now, he said, although the information, gleaned from rescued refugees, was not confirmed.