Updated

Up to 500 refugees are feared dead in a shipwreck in the Mediterranean Sea last week after a boat capsized while carrying “hundreds of people in terribly overcrowded conditions," the U.N. refugee agency announced Wednesday.

UNHCR said the disaster unfolded in the waters between Italy and Libya, based on accounts from 41 survivors who were rescued on April 16 by a merchant ship, The Associated Press reported.

The survivors said they had been among 100 to 200 people who left a town near Tobruk, Libya, on a smugglers' boat last week. The agency said Wednesday that "after sailing for several hours, the smugglers in charge of the boat attempted to transfer the passengers to a larger ship carrying hundreds of people in terribly overcrowded conditions."

The agency added, "at one point during the transfer, the larger boat capsized and sank."

"My wife and my baby drowned in front of me," a survivor from Ethiopia told the BBC.

A Somali survivor said the wooden boat that capsized was around 90 feet in length and already had around 300 people on it before the hundreds from his ship were asked to board.

"I was one of the few who managed to swim back to the smaller boat," the Ethiopian survivor – who was identified only as Muaz – told the BBC.

Witnesses said they continued the journey on the smaller boat, but the engine broke down amid suspicious of sabotage by the trafficker. The trafficker then hopped onto a small boat that was tied to the ship’s side and headed back toward Libya, the BBC reported.

"RESCUE 16 April 2016" was painted in red on the roof of the boat, which was later spotted by a cargo ship which brought the survivors to Greece.

Barbara Molinario, a Rome-based spokeswoman for UNHCR, said details remained unclear and said its staffers didn't want to press the survivors too hard "as they are still very tried by their experience."

The statements offered the most official comment yet following repeated news reports about the incident in recent days.

Somalia's president, prime minister and parliamentary speaker on Monday issued a joint statement over an unconfirmed report about the incident. Reports of the drownings circulated among families and on social media, but they hadn't been confirmed by coast guard authorities in Italy, Greece, Libya or Egypt.

More than 1 million migrants and refugees crossed the Mediterranean last year — mostly refugees from war in Afghanistan, Iraq and Syria fleeing to Greece, and the European Union, via Turkey. However, the longer Libya-Italy route has traditionally seen more deaths.

Facing internal divisions, the EU has struggled to cope with the influx, and UNHCR on Wednesday reiterated its longstanding call for more "regular pathways" to Europe such as with resettlement and humanitarian admission programs, family reunification, private sponsorship and student and work visas.

Rights groups have repeatedly slammed a new Turkey-EU deal to curtail the flood of refugees into Europe, raising questions about the safety of Syrian refugees on both sides of the Turkish border.

Earlier Wednesday, Human Rights Watch urged Turkey to allow Syrians displaced by government shelling to cross the border to safety. The advocacy groups said the Syrian army hit two migrant camps on April 13 and 15, triggering an exodus of 3,000 people.

Last week, the rights group said Turkish border guards had shot at Syrians escaping an Islamic State offensive. Turkey, home to 2.7 million Syrian refugees, rejects the claim and says it has an open-door policy toward migrants, but new arrivals are rare.

The rights group says tens of thousands of civilians are trapped along Turkey's border.

The Associated Press contributed to this report.