Thousands of protesters, angry at the government's mishandling of Covid-19, had flooded onto the streets and clashed with police on Sunday.
President Kais Saied announced he would take charge with help from a new prime minister, saying he intended to bring calm to the country.
But opponents branded his move a coup.
"We have taken these decisions... until social peace returns to Tunisia and until we save the state," Mr Saied said in a televised address after an emergency security meeting at his palace.
