Violence broke out as migrants threw rocks, bottles and gas canisters at police in Rome. Officers used water cannons to quell resistance from asylum-seekers as human rights groups protested the authorities' use of force.
Officials said at least 13 people were injured and two were taken into custody when migrants and police clashed in Rome on Thursday.
The dawn raid in a piazza near the main train station came just days after police cleared most of the 800 migrants, almost all of them asylum-seekers, from an adjacent building - where many have been squatting since 2013.
Police issued a statement saying the operation was necessary because the migrants in the piazza had refused city-organized housing and because of the risk posed by cooking gas canisters and other flammable materials.
For the sake of guarding against terrorism, officials said it was important for migrants to leave the square and move into housing provided by the city.
Asylum-seekers who had been allowed to remain temporarily in a nearby building - most of them women and children - hung signs out of its windows saying "We are not terrorists." They were also evicted by police.
UNICEF, the UN refugee agency and humanitarian aid organizations protested the Italian police tactics, complaining that they were executed without warning - and that there is a shortage of adequate housing in Rome for the migrants.
Rights activists also complained that families would be separated by the new housing arrangements and lamented that children would be uprooted from their schools.
Doctors Without Borders, also referred to by their French acronym MSF, issued a statement expressing disappointment that the situation was not resolved peacefully.
"It is a shame that the absence of alternative housing solutions brought about a violent situation," MSF said in a statement, calling for "dignified solutions" for those who have been removed.
MSF posted photos of the clashes on Twitter and criticized the "indiscriminate use of violence."
The group also pointed out there were no ambulances nearby to help the injured, leaving the task to the MSF volunteers. They treated 13 injured, mostly for cuts and fractures; one elderly woman fainted after being hit by a jet of water.
Italy is struggling to meet the demand to house migrants, with nearly 100,000 arriving so far this year. Much of Europe has refused to help Italy, leaving the country to fend for itself. Most of those rescued at sea attempted the journey in rickety boats provided by smugglers.
Tougher border controls are preventing many migrants from continuing their journeys to preferred destinations in northern Europe.
bik/sms (AP, Reuters, dpa)