In the south-eastern Tunisian city of Zarzis, shops and government offices were closed, along with health services, except for emergency cases, on Tuesday (Oct 18).
Protesters demanded a renewed search for relatives who went missing in a failed migration attempt.
Chanting, slogans like the "people want the truth", thousands once again took to the streets.
The pressure piling on authorities prompted the president to ask his Justice Minister to open an investigation.
"I assure you that this is a historic strike (in the city of Zarzis, ed)", local activist Ezzedine Msalem, said.
"The state must reveal the truth. Today, we want to know the truth. It is a state crime that was perpetrated against the inhabitants of Zarzis with the burial (of bodies found at sea -- believed to be passengers from the boat -- in a cemetery for foreign migrants, ed) without identifying them before, nor having done any DNA analysis."
Alleged burial without identification
Four weeks ago, 18 Tunisians boarded a boat headed for Italy, before it sank.
Four people, suspected of being missing Tunisians, were buried in a nearby cemetery for foreign migrants -- allegedly without efforts to identify them.
Those bodies have since been exhumed for identification, while another two bodies believed to be Tunisians were found.
One of the country's largest unions, the UGTT trade union federation voiced support for the strike and demanded an inquiry into the rescue effort and how the bodies were buried.
The Tunisian Human Rights League said authorities had "not devoted the necessary resources to search and rescue operations in a timely way" and called for an inquiry into the burials.
Tunisian authorities intercepted nearly 200 migrants attempting to reach Europe over the weekend, the defense ministry said Tuesday.
According to official figures, more than 22,500 migrants have been intercepted since the start of the year, around half of them from sub-Saharan Africa.