Bigger boats, with more people on-board, are partly to blame for an increased death toll in the Mediterranean.
Italian police have also picked up 16 alleged human traffickers at sea.
At least 1,000 migrants drowned in the Mediterranean Sea this past week as the crush of refugees desperate to reach Europe continues, according to the International Organization for Migration (IOM).
The IOM reported on Tuesday that 500 people died last Thursday and approximately 250 more on both Wednesday and Friday.
A further 50 people were still missing, according to Flavio Di Giacomo, an IOM spokesman in Rome.
"If we add these numbers up, we are well above 1,000," he said.
The UN High Commission for Refugees (UNHCR) put the number of dead at 880, but acknowledged the death toll could be higher.
UNHCR spokesman William Spindler said his agency learned from survivors "that 47 people were missing after a raft carrying 125 people from Libya deflated.
Eight others were reported separately to have been lost overboard from another boat, and four deaths were reported after fire aboard another."
Italian authorities have rescued approximately 13,000 people along the Libya-Italy sea route.
The UNHCR put the odds of drowning during a crossing of the North Africa to Italy route at one in 23.
For the whole of the Mediterranean, 2,510 people have died this year, compared with 1,855 last year.
Di Giacomo, the IOM spokesman, said the increase is due, in part, to larger, wooden, boats that can carry as many as 700 people.
Thousands of desperate people
More than 200,000 people have made the perilous trip across the Mediterranean since the start of the year.
Among them, nearly 47,000 arrived in Italy, according to the UNHCR.
Almost all of the rest travelled from Turkey to Greece before the border was closed in April.
Migrants 'deserve protection'
Another IOM spokesman, Joel Millman, said that while many migrants come seeking jobs rather than refugee protection, many of them end up becoming sex slaves in Europe.
Speaking from Geneva, he said, they "deserve protection."
Migrants, however, were not the only ones picked up at sea this week.
Italian police said they picked up 16 alleged people-smugglers when the intercepted a boat off the coast of Libya: 11 from Morocco, two Palestinians, and one each from Ethiopia, Gambia and Egypt.
The men, aged 19 to 36, were charged with abetting illegal migration.
Authorities in Catania, Sicily, where the arrests were made, said the suspects extracted payments of up to 1,000 euros ($1,116) from each person who wanted to reach Europe.
Before the sea journey, the migrants were held captive for up to 45 days, and were only fed bread and water once a day, according to Italian police.
Michelangelo Patane, a prosecutor in Catania told a press conference that the victims were also beaten with straps.