Migrants try to jump in the water before their boat overturns off the Libyan coast on May 25. (Italian navy via AP/AP)

The number of people who have died this year trying to cross the central Mediterranean and reach Italian shores has doubled in the past week following a series of especially disastrous shipwrecks, aid organizations said Tuesday.

More than 1,000 people have perished in the past week while seeking passage from the coast of war-scarred Libya, about the same number who had died along the North Africa-to-Italy route earlier in 2016, according to the International Organization for Migration (IOM).

The Office of the U.N. High Commissioner for Refugees (UNHCR) gave a slightly lower figure for the week, recording 880 people drowned. But the refu­gee agency emphasized that its estimate was conservative.

Both groups’ figures significantly exceed the 700 people who were reported to have died during the past week as of Sunday.

The higher figures reflect more detailed information from survivors who were rescued at sea. The tolls make the past week one of the deadliest in the four years that people fleeing war, oppression and poverty have been streaming into Europe, bringing a crisis to the continent’s shores.

A Sea-Watch humanitarian organization crew member holds a drowned migrant baby, during a rescue operation off the coast of Libya on May 27. (Christian Buttner/Eikon Nord via AP)

The surging death toll marks an ominous turn as warmer seas traditionally draw ever-larger numbers of people to attempt the passage on rickety fishing boats that are ill-equipped for the task.

“Smugglers are packing people on boats that are barely seaworthy and that in many cases are not meant to make the crossing,” UNHCR spokesman William Spindler said at a briefing in Geneva.

But Spindler said it was “shameful” for European leaders to focus primarily on stopping smugglers while doing little to open up legal routes for those seeking sanctuary on the continent.

“We need to crack down on smugglers. But simply doing that is not going to work if we don’t offer people an alternative,” Spindler said. “The reason why so many people are taking to sea in these conditions is that they have no choice.”

Spindler singled out for criticism a European Union plan to relocate 160,000 asylum seekers from Greece and Italy. Fewer than 2,000 have been resettled since the plan was launched late last year.

More people than that have drowned this year while attempting to make the sea crossing. Including deaths on the eastern Mediterranean route, from Turkey to Greece, the 2016 toll now stands at roughly 2,500 — about 30 percent higher than it was at this time last year, according to the IOM.

The central Mediterranean route has been the most treacherous, by far. Spindler estimated the chance of dying along the journey from North Africa to Italy at 1 in 23.

Last year, the main route to Europe shifted from the central Mediterranean to the sea’s eastern edge as people began using rubber dinghies to cross in record numbers from the Turkish coast to the Greek islands. The far-shorter journey made for a relatively less treacherous crossing.

But Europe effectively shuttered that route this spring, blocking people from traveling deeper into Europe from Greece and beginning to deport new arrivals back to Turkey.

With those moves, the more dangerous central route has again become the most common.

However, there is little evidence that the same people who otherwise would have traveled via Greece are now trying to reach Italy. The eastern Mediterranean route has been dominated by Syrians, Iraqis and Afghans. The central route, by contrast, is populated largely by sub-Saharan Africans, especially Nigerians, Gambians and Somalis.

The total number of arrivals in Italy is about the same it was at this time last year.

The UNHCR said Tuesday that smuggler networks are sending people from sub-Saharan Africa through the continent’s interior to Libya. Once there, many are abused before being allowed to continue on their journeys. “Some women have told us they were subject to sexual slavery in Libya,” the group said.

The migrants are also forced aboard vessels that are conspicuously unsafe.

In last week’s deadliest disaster at sea, the IOM reported that migrants balked at boarding a vessel that lacked an engine and had to be towed by another boat. When the engineless boat began to take on water Thursday, “the captain of the towing boat then cut the tow line,” the IOM reported, citing witness accounts. “The second vessel continued to take on water and eventually capsized.”

About 500 people drowned.

In another capsizing, this one on Friday, rescuers from the Italian navy and the German aid group Sea-Watch managed to pluck 135 people from the water. But at least 45 others died.

Among them was a baby who, according to a Sea-Watch rescuer who gave his name only as Martin, looked as “if it were alive.”

But when Martin looked closer, he noticed the “shining, friendly but motionless eyes” and the body that looked like a doll with its “arms and tiny fingers stretched toward the sky.”

“Nobody in our boat talked,” he recalled in an email. “Only six hours ago, this baby had still been alive.”

Martin said that most of the other drowned refugees were women; two of them appeared to have been pregnant.

The rescuer, a father who usually works as a music therapist in Germany and was volunteering with Sea-Watch, said of his reaction to recovering the baby's corpse, “I wanted to scream, but I decided to sing instead, in order to calm myself and the baby which should never have died — and to give some kind of expression to this incomprehensible, heartbreaking moment.”

Rick Noack contributed to this report.