More than 50 people die in Mediterranean crossings
Tunisian authorities said 47 bodies were recovered off the country's southern coast, close to the city of Sfax, while 68 people were rescued.
"The coastguard and the navy continue their search with the support of a military plane," the interior ministry said in a statement.
The International Organisation for Migration (IOM) said there were more than 70 survivors from the shipwreck, with spokesman Flavio Di Giacomo cautioning on Twitter that the final number of missing was still uncertain.
"There were around 180 of us on board the boat... which sank because of a leak," a survivor told Tunisia's Mosaique FM radio, describing the boat as around nine metres (30 feet) long.
Tunisians and migrants regularly try to cross the Mediterranean to seek a better future in Europe, with 120 mainly Tunisians rescued by their navy in March after trying to reach Italy.
In October, a collision between a migrant boat and a Tunisian military ship left at least 44 dead, in what Prime Minister Youssef Chahed called a "national disaster".
The latest shipwreck is the most deadly in the Mediterranean since February 2 when 90 people drowned off the coast of Libya, according to the IOM.
Across the Mediterranean, nine migrants including six children drowned when their vessel sank off the coast of Turkey.
The group were travelling in a speedboat intending to head illegally to Europe, when the boat hit trouble off the coast of the southern Antalya province, state media reports said.
Turkey was the main sea route for migrants to Europe in 2015, when more than a million people crossed to Greece.
That year 3,771 people were recorded as dead or missing in the Mediterranean by the United Nations refugee agency.
So far this year, 32,601 migrants and refugees have survived the sea crossing and 649 have been recorded as dead or missing.
A deal struck with the EU in 2016 has drastically reduced the amount of people trying to make the sea crossing, although observers say the numbers have been ticking up again in recent months.
Italy marks policy shift
The focal point for Mediterranean migration in recent years has been Italy, where more than 700,000 migrants have arrived since 2013.
On Sunday the country's new hardline interior minister, Matteo Salvini, headed to Sicily, one of the main landing points for those rescued at sea, to push his anti-immigration agenda.
His predecessor signed a controversial deal with authorities and militias in Libya - the key departure point on the route to Italy - which has driven down overall arrival numbers by 75 percent since last summer.
But Salvini has pledged to go further still, vowing to cut the number of arrivals and speed up deportations.
"The good times for illegals is over - get ready to pack your bags," he said Saturday at a rally in Italy's north.
The latest arrivals, some 158 people, were rescued by a humanitarian boat and reached southern Sicily on Friday.
Meanwhile Spanish maritime rescue units said Sunday they have picked up 240 migrants since the start of the weekend, with one person reported drowned.
Migration will be high on the agenda Tuesday when EU interior ministers meet in Luxembourg and discuss the bloc's contested Dublin rule, under which would-be refugees must file for asylum in the first member country they enter.
Many of those landing on the Mediterranean coast see their arrival point as a pathway to their final destination, but the Dublin rule and tightening border checks have meant migrants are increasingly stuck in southern Europe.