Thirty people were feared drowned after the boat they were travelling in from Libya capsized in bad weather on Sunday, Italy's coastguard said.
The tragedy follows a 26 February shipwreck near the southern region of Calabria, in which at least 79 people died.
Alarm Phone, a charity that picks up calls from migrant vessels in distress, blamed Italy for not sending its coastguard earlier despite being repeatedly alerted on Saturday that the boat was in trouble.
"Clearly, the Italian authorities were trying to avoid that the people would be brought to Italy, delaying intervention so that the so-called Libyan coastguard would arrive and forcibly return people to Libya," it said in a statement late on Sunday.
Italy's coastguard said the capsizing occurred outside the Italian Search and Rescue area (SAR), and Foreign Minister Antonio Tajani said Rome was doing all it could to avoid shipwrecks.
No patrol boats available
The vessel, travelling in the direction of Italy, capsized about 110 miles northwest of the Libyan port of Benghazi, according to the Mediterranea Saving Humans charity.
According to a phone conversationtranscript shared by German charity Sea-Watch, a duty officer at the Libyan Joint Rescue Coordination Centre said that at the time there were no patrol boats that could be sent from Benghazi.
Rome requested merchant ships in the area to join the rescue efforts, the Italian coastguard said. But the migrant vessel capsized during an attempt to transfer the passengers to the FROLAND merchant ship on Sunday morning, it added.
Rome's ability to rescue migrants at sea has come under scrutiny following last month's shipwreck, and the issue is piling pressure on the rightwing government which took office last October promising to curb the influx of migrants.
Instead, arrivals have surged, with over 20,000 people reaching Italy by sea this year so far, more than triple the around 6,150who arrived in the same period of 2022, official figures show.
Over 4,500 people reached Italy from 9-11 March alone.
The Italian government on Monday said Russian mercenary group Wagner, which has been accused of operating in several African countries including Libya, was to blame for the surge in crossing attempts as part of Moscow's strategy to retaliate against countries supporting Ukraine.