World News

ROME — Dozens of migrants — possibly more than 100 people — drowned in the Mediterranean Sea while trying to reach Europe this month after their boat sank and passengers waited in the water for hours until a rescue ship arrived, according to Doctors Without Borders.

European airplanes dropped lifeboats at the scene, survivors said, but Italy did not dispatch a ship. Instead, it deferred to Libya. And although the Libyan Coast Guard rescued nearly 300 of the stranded migrants, the circumstances raised questions about whether more people might have been saved.

Passengers said disaster had struck near the coast of Malta, a small island nation that is closer to Italy than to Libya, and that they had notified Italian officials of their coordinates. It was not clear whether Malta sent a ship, but none arrived in time to reach survivors.

“Why didn’t the Italian Coast Guard intervene?” asked Sara Creta, a Doctors Without Borders humanitarian aid worker in North Africa. “Why did they send in the Libyan Coast Guard? I think it’s important to know that.”

The Italian Coast Guard said the “rescue took place in the Libyan search and rescue area, and was coordinated by the Libyan authority, which sent its ships to the area after it had assumed the coordination of the operations.”

The area of Libyan responsibility was established in a 2017 agreement as Italy significantly hardened its stance toward migrants trying to make their way to Europe.

Doctors Without Borders, which treated the survivors, said that Libya had put 276 of them into what the aid group described as “indefinite arbitrary detention,” which has become common practice as Libya cooperates with European efforts to stem the flow of migrants from Africa and the Middle East. Some of those rescued suffered chemical burns from exposure to fuel that spilled from their boat into the water.

Since Italy elected a new, populist government this year on a wave of anti-immigrant sentiment, officials have vowed that the country will no longer take in people who are trying to make unauthorized entry. It has even denied entry to rescue ships.

But some migrants say that a recent resumption of violence in Libya’s capital, Tripoli, after years of chaos and warfare, prompted them to attempt the perilous crossing. One woman with two children said she feared being trafficked if she remained in Libya, while a man who had lived there for two years spoke of his fear of the tanks and soldiers in the streets, Doctors Without Borders said.

The International Organization for Migration, which is affiliated with the United Nations, says that since the start of 2014, almost 13,000 people have died trying to cross the Mediterranean. The United Nations also reported this month that the sea journey is now deadlier than at any point since the peak of the European migration crisis in 2015, even as unauthorized migration along the route has fallen to its lowest level in the same period.

In this latest deadly crossing, two rubber boats left the Libyan coast together in the early hours of Sept. 1, filled to bursting with hundreds of migrants. The engine of one boat failed, leaving it adrift, while the other began deflating around midday, Doctors Without Borders said based on survivors’ accounts.

The passengers used a satellite phone to send a desperate SOS as people began slipping from the shrinking boat into the water. The Italian Maritime Rescue Coordination Center “received an alert regarding the event and informed the search and rescue authority with jurisdiction over that area of the sea,” the Coast Guard said.

One survivor told Doctors Without Borders that the migrants could not swim, and that only a few had life jackets. The migrant said that the boat that sank carried 185 people, including 20 children, and only 55 had survived, indicating a death toll of 130, the aid group said. It said that other passengers were less precise but agreed that more than 100 people were missing and feared dead.

The International Organization for Migration said the Libyan authorities had reported only two bodies found and 25 people missing.

The number of people from the Middle East and Africa trying to reach safety and economic opportunity in Europe surged in 2015 and 2016, largely driven by the war in Syria. It has subsided since then, but how to handle those already in Europe, and those seeking to come, remains a political flash point across the continent.

The new United Nations human rights chief, Michelle Bachelet, said Monday that she would send investigators to Italy to examine the country’s treatment of migrants. Italy’s foreign ministry on Tuesday dismissed that move as unfounded.

Many survivors of the Sept. 1 disaster were irate that they had been returned to Libya, and Doctors Without Borders said it was unable to give adequate medical treatment to many of those rescued, who include infants, pregnant women and people with serious medical conditions.

In the first eight months of this year, Doctors Without Borders said, more than 13,000 migrants picked up at sea have been returned to Libya and put into detention.

Ms. Creta said that detention could last months or even a year.

“It’s arbitrary,” she said. “No one knows how long they will be there.”