GENEVA (Reuters) - More than 400 migrants and refugees drowned in early 2023 while attempting to cross the central Mediterranean from North Africa to Europe, the most fatalities in the past six years over a three-month period, a United Nations agency said on Wednesday.

The International Organization for Migration (IOM) documented 441 migrant deaths between January and March on the world's deadliest migration route, in what it said was likely an undercount. Around half of those deaths were linked to delays in state-led rescue efforts and, in one case, the absence of any rescue mission, it said.

"The persisting humanitarian crisis in the central Mediterranean is intolerable," said IOM Director General António Vitorino. "With more than 20,000 deaths recorded on this route since 2014, I fear that these deaths have been normalized. States must respond."

Thousands of mostly African migrants embark on the dangerous journey from the shores of Libya and Egypt, often in small, inflatable boats, in search of a better life in Europe.

This "central" route is distinct from the Western crossing from Morocco to Spain.

Frequently, the ships sink, as in the case of a deadly shipwreck off the southern Italian region of Calabria in late February that killed at least 72 migrants.

Italy's cabinet on Tuesday announced a state of emergency on immigration following a "sharp rise" in flows across the Mediterranean, in a move aimed at better management of migrant arrivals and repatriation facilities.

(Reporting by Emma Farge; Editing by Bernadette Baum)