January to March 2023 was the deadliest first quarter for migrants crossing the central Mediterranean since 2017, the United Nations said Wednesday, with 441 lives lost attempting to reach Europe.

Noting the most fatalities in the past six years over the first three-month period of the year, the International Organization for Migration (IOM) said on Wednesday that the toll of 441 known deaths was likely an undercount of the true number, adding that delays in state-led search and rescue (SAR) operations were a factor in several fatal incidents.

"The persisting humanitarian crisis in the central Mediterranean is intolerable," said IOM chief Antonio Vitorino. "States must respond. Delays and gaps in state-led SAR are costing human lives."

The IOM said delays in such rescues were a factor in at least six incidents so far this year, leading to the deaths of at least 127 people.

The UN agency's Missing Migrants Project is also investigating several reports of cases in which boats were reported missing, where there are no records of survivors, no remains and no SAR operations.

The fates of more than 300 people aboard those vessels remain unclear, the organization said.

"Saving lives at sea is a legal obligation for states," said Vitorino.

"We need to see proactive, state-led coordination in search-and-rescue efforts. Guided by the spirit of responsibility sharing and solidarity, we call on states to work together and work to reduce loss of life along migration routes."

Countries need to support the life-saving efforts of NGOs and end the "criminalization, obstruction and deterrence" of those who do come to the rescue, the IOM said.

The agency also called for tougher action to dismantle criminal smuggling networks and to prosecute those responsible for "profiting from the desperation of migrants and refugees by facilitating dangerous journeys".

(With input from AFP)