The UN refugee agency says not enough is being done to save the lives of the rising number of migrants trying to cross the Mediterranean to Europe.
A UNHCR spokesman called on the EU to step up its rescue system, after a migrant boat capsized off Libya on Sunday, with 400 feared dead.
Libya's coastguard says it expects more attempted crossings later this week.
Hundreds of thousands of people have made the perilous crossing in recent years, fleeing poverty and conflict.
Hundreds more migrants rescued from boats in the Mediterranean are due to arrive in Sicily later on Wednesday.
Almost 10,000 have been picked up in recent days, and more boats are heading for the Italian coast.
Italy's interior ministry has instructed officials throughout the country to be prepared to house the new arrivals, many of whom are children.
UN officials say well over 500 people have died since the start of the year, 30 times more than in the same period last year.
Over 280,000 people entered the EU illegally last year, many fleeing conflict in Syria and repression in Eritrea.
The Italian coast guard rescued 144 people from the capsized boat on Monday and launched an air and sea search operation in hopes of saving others.
Nine bodies have already been recovered, but no more survivors have been found since then.
UNHCR spokesman Federico Fossi told the BBC there was no indication that the numbers risking their lives to come to Europe would drop soon.
"There are still people fleeing from wars and persecution in countries such as Syria, dictatorships in countries such as Eritrea," he said.
"People will keep crossing and the UNHCR repeatedly called on the European Union to step up a strong search and rescue mechanism in order to save people's lives," Mr Fossi added.
Migrants in Libyan jail
The BBC's Quentin Sommerville is at a detention centre for would-be migrants in Misrata, Libya - among them this 14-year-old from Eritrea (below). "Is this a jail? Are we refugees?" some of the migrants ask. They say they have been held there for seven months.
Last year, 170,000 migrants crossed the Mediterranean to Italy and as many as 3,500 died while making the journey, officials say.
The Italian government's maritime rescue operation was scaled back, amid concerns that it was encouraging migrant crossings, and a more limited EU border security operation took over.
EU migration commissioner Dimitris Avramopoulos told the European Parliament: "The unprecedented influx of migrants at our borders, and in particular refugees, is unfortunately the new norm and we will need to adjust our responses accordingly."
Since the fall of Muammar Gaddafi in 2011, Libya has been without a stable government allowing trafficking networks to thrive.
On Friday, humanitarian organisation Medecins Sans Frontieres announced it would operate a search and rescue mission in the Mediterranean between May and October.