Migrants arriving on boats in southern Italy say 81 other people travelling with them have died or gone missing during their sea journeys from north Africa, the UN refugee agency said on Wednesday.
A group of 27 migrants picked up on Tuesday by Italy's naval rescue mission and brought to the town of Catania said there had been 75 other people on their boat, who were feared drowned, the UNHCR said in a statement.
Other migrants arriving in Sicily's Porto Empedocle said two of the party they travelled with had died and four had disappeared.
Authorities said the death toll on another packed fishing boat, discovered by an Italian rescue mission on Monday, had reached 45. The victims are believed to have suffocated.
All those found dead on Monday by the "Mare Nostrum" or "Our Sea" naval operation were men from Subsaharan Africa, the U.N. said.
The UNHCR says around 500 migrants have died so far this year in the Mediterranean. Many were fleeing war in Syria, forced conscription in Eritrea, or poverty in other countries in Africa.
Italy's navy tweeted that Mare Nostrum had rescued 236 migrants, including 35 women and 54 minors, on Wednesday.
Southern Italy has long attracted flows of seaborne migrants, and calm weather has contributed to a surge over recent weeks.
The number reaching Italy this year, many of whom pay a trafficker more than $1,000 for the trip, has already matched the annual record of 62,000 set in 2011 during the Arab Spring uprisings.
Mare Nostrum costs around 9 million euros ($12.3 million) a month, and Italy has called for more help from the European Union. The EU said on Monday it was making 4 million euros of emergency funding available to Italy.
The influx of migrants has revived support for Italy's anti-immigration Northern League party, whose leader Matteo Salvini called on Prime Minister Matteo Renzi and Interior Minister Angelino Alfano to resign over the issue on Wednesday.
"The jackets of the people in power are covered with more and more blood, the cemeteries are filling up, the Italians' pockets are emptying," Salvini wrote on Facebook.
($1 = 0.7331 Euros)
(Reporting by Isla Binnie; additional reporting by Wladimiro Pantaleone in Sicily; editing by Andrew Roche)