At least 48 migrants died after their boat capsized off the eastern coast of Tunisia, the Tunisian government says.
Sixty seven others - from Tunisia and elsewhere - were rescued by the coastguard.
The country has become an important new route for migrants trying to make the crossing to Europe in the past year.
This comes after moves against human traffickers in Libya, who have regularly enslaved, tortured or murdered migrants.
The latest boat to go down off Tunisia was packed with about 180 people, about 100 whom were Tunisian, the country's interior ministry said.
The boat was five miles from the Kerkennah Islands and 16 nautical miles from the city of Sfax, the ministry said.
Rescue operations were suspended late on Sunday but will resume on Monday morning, officials said.
One survivor told Reuters that the captain had abandoned the boat after it started sinking to escape arrest by the coast guard.
Another survivor, Wael Ferjani, said the boat had a maximum capacity of 90 people - only about the half the number actually on board.
"We could touch the water with our hands, and water was coming into the boat," he said.
"Those who could escape fled, others drowned, we stayed there until almost five in the morning, then fishermen came to help us, and then the army arrived."
Unemployed Tunisians and other Africans often seek to cross the Mediterranean sea in makeshift boats from Tunisia to Sicily in Italy.
The deaths come on the same day Italy's new Interior Minister Matteo Salvini said on a visit to Sicily that the island must stop being "the refugee camp of Europe".
Meanwhile, the Turkish coastguard said nine Syrians including six children drowned in a similar accident off the coast of Antalya province.
The oldest child to drown was aged 14 and the youngest was aged three, the Anadolu news agency reported.
Six adults were reportedly rescued. They included a couple five of whose children died in the incident.
More than 32,000 people have reached Europe by sea so far this year, the International Organization for Migration (IOM) says, and 660 people have died attempting the crossing.
