The deployment of 500 troops aims to restore order after Saturday and Sunday of violence where police used teargas and water cannon to disperse violent groups operating on the fringes of an initially peaceful protest.
Related demonstrations over housing costs and urban unrest prompted thousands to gather in Lisbon's central Rossio square to re-establish a tent camp, aligning with similar protests in central Madrid.
Opposition politicians have accused the government of using security as a propaganda tool, arguing that authorities fail to address core issues such as education, housing, and living conditions in these marginalised areas.
The Italian press agency Ansa reported that security measures under consideration specifically target second-generation immigrant youths, known locally by the slang term maranza used to describe gangs from marginalised areas.
Police in Milan detained 271 young people following weekend unrest that involved hooded youths setting bins ablaze, ransacking shops, and smashing windows around the city's cathedral.