GENEVA — The treacherous Mediterranean Sea crossing from Libya to Italy claimed the lives of at least 1,083 migrants over the past week – mostly because barely seaworthy smuggling boats foundered and sank despite calm seas and sunny skies, a migration agency said Tuesday, citing new accounts from survivors.

The staggering death toll could foreshadow more disasters in coming months as the region gears up for the traditional summer-fall spike in human trafficking as the weather improves and seas grow warmer. Aid officials say it also suggests that Libyan smuggling gangs are using even riskier tactics to profit from the torrent of people desperate to reach the safety and economic promise of Europe.

Making matters worse, the tally is only from the capsizings or shipwrecks known to authorities, who acknowledge they don’t have precise information on how many people are being jammed into unsuitable vessels and swallowed up by the vast waters of the southern Mediterranean.

Two Eritreans among the hundreds of shipwreck survivors brought to Italian ports last week described being haunted by the number of women and children on their capsized boat who did not survive. They could still hear the cries of the children as the ship sank Thursday, they said.

“I started to cry when I saw the situation and when I found the ship without an engine. There were many women and children,” said 21-year-old Filmon Selomon who plunged into the sea to save himself. “Water was coming in from everywhere, top, bottom.”

“The children were crying and the women,” said Habtom Tekle, a 27-year-old Eritrean. “At this point I only tried to pray. Everybody was trying to take the water out of the boat.”

The International Organization for Migration said Tuesday that 62 people were confirmed dead and another 971 were missing and presumed drowned in nine separate emergencies since May 25 on the Libya-to-Italy sea route.

William Spindler, a spokesman for the U.N. refugee agency, told reporters in Geneva that this year was already proving to be “particularly deadly” on the Mediterranean, with some 2,510 lives lost compared to 1,855 over the same period a year ago.

IOM spokesman Joel Millman told The Associated Press that last week’s toll was the largest in a single week since mid-April of last year, when 1,226 people drowned or went missing, most in two deadly sinkings.

In the deadliest of last week’s shipwrecks, 500 people remain missing after a boat without an engine capsized on Thursday as it was being towed by another boat loaded with some 800 people, the agency said. A day earlier, a sinking left some 250 people missing and five confirmed dead. By Saturday, 45 people were confirmed dead and 215 missing in a shipwreck off Reggio Calabria, Italy.

Six smaller incidents left another 68 people dead or missing last week, IOM said.

Spindler gave a somewhat lower toll, saying UNHCR estimates that at least 880 people were believed dead. He noted such estimates were an inexact science and UNHCR figures tend to be “conservative.”

IOM said nearly 19,000 migrants arrived in Italy by sea in May.