Tunisian President Kais Saied warned the country's powerful trades union federation on Friday against inviting foreigners to a planned weekend demonstration.
The comments by Saied came a day after the UGTT union federation said a senior official from one of Spain's main unions had been denied entry at Tunis airport.
Marco Perez Molina had planned to attend the union's protest against Saied's "one-man rule".
"The UGTT is free to organise demonstrations... but it is not free to invite foreigners to participate in them," Saied said in a video published on the presidency's official page.
He added that the presence of foreigners at protests "is totally unacceptable" and that Tunisia "is not a domain without a master."
Saied has pushed through sweeping changes to the North African country's political system, concentrating near-total power in his office since he froze parliament and sacked the government in a July 2021 move against the sole democracy to emerge from the Arab Spring uprisings.
On February 18, he ordered the expulsion of Europe's top trade union official, Esther Lynch. She heads the European Trade Union Confederation and had spoken at a UGTT rally in solidarity with Tunisian workers.
On Thursday, Tunisian authorities said they had banned a protest planned for Sunday by the country's main opposition coalition, arguing that senior members are suspected of crimes against the state.