Fresh testimony Wednesday from survivors of a deadly shipwreck in the Mediterranean raised the likely death toll for the past 48 hours to 240 people, confirming fears of rescuers who had warned dozens probably died.
The new tally is based on information gathered by the UN's refugee agency (UNHCR) from 15 survivors, who said some 135 people had drowned or lost when a dinghy sank on Monday.
Some 95 others were feared dead after another dinghy sank on Tuesday.
Nine bodies have been recovered in total after both incidents, while a 10th person was seen to have drowned but could not be pulled from the sea by rescue teams.
Monday's survivors arrived early Wednesday in the port of Catania in Sicily, where they spoke of their ordeal.
"The survivors told us that there were about 150 people on board, so there would be about 135 missing," UNHCR spokesman Iosta Ibba told AFP.
The migrants are overwhelmingly from sub-Saharan Africa.
The latest deaths will lift the total number of migrants who have died trying to cross the Mediterranean this year to just over 4,500, according to a UNHCR count based on bodies recovered and survivor accounts.
The Malta-based charity MOAS, which deploys two rescue boats in the area, said Wednesday that "it is almost certain that the true death toll is much higher than the recorded figure as it is highly likely that many boats sink without ever being reported".
The rate of departures from the North African coast continues unabated despite worsening weather in the Mediterranean, with over 2,700 people having been rescued from crowded and unseaworthy dinghies off Libya since SatuAlso - srday.
Video footage released by MOAS showed survivors on board one of its rescue vessels howling with grief as the body of a victim is carried on board, wrapped in a white sheet.
The charity blamed "the changing approach of smuggling networks" which it said showed "an attempt to maximise opportunity and meet demand on the part of the smugglers".
"Whereas in past years, crossings were organised in more manageable trickles, perhaps a few a day, this year our crews have seen departures organised in large waves," it said in a statement.
"Despite tireless efforts to save lives by both civil society and European navies... search-and-rescue efforts in the Mediterranean are more challenging than ever," it added.
Over 167,000 people have been brought to safety in Italy since the start of the year, according to the interior ministry. The figure has already passed the 153,000 number recorded in 2015 and is closing in on the 170,000 figure recorded in 2014.