The coastguard rescued five people and was searching for about 20 others who were still unaccounted for, the official said.
“The boat sank about six miles from the coast of Sfax. Twenty bodies were recovered, five others were rescued, and all are from sub-Saharan Africa,” the security official, Ali Ayari, said.
Around 45 people were on the boat when it sank, he added.
The coastline near the Tunisian port city of Sfax has become a major departure point for people fleeing conflict and poverty in Africa and the Middle East and searching for a better life in Europe.
Countries including Italy and Malta have seen an increase in sea arrivals this year from Tunisia — where high unemployment and uncertain socioeconomic conditions have driven migration — and from Libya, where conflict and war was a major factor, according to figures from the United Nations High Commissioner for Refugees (UNHCR).
Thursday’s deaths adds to the already long list recorded this year, even with Covid-19 travel restrictions in place.
The boat was reported to be carrying over 120 people, among them women and children, according to the IOM.
Soda called for a change in the “unworkable approach to Libya and the Mediterranean, including ending returns to the country and establishing a clear disembarkation mechanism followed by solidarity from other states.”
“Thousands of vulnerable people continue to pay the price for inaction both at sea and on land,” he said.
Migration-related deaths are often under reported and unrecorded, according to the IOM, who also said that the pandemic has made it more difficult to collect that data.
CNN’s Emma Reynolds and Sharon Braithwaite contributed to this report.